INFORMATIO INFOR MATION N TECHNOL TE CHNOLOGY OGY NOTES N OTES
DATA AND INFORMATION
Data processing cycle Validation Checks Input device Storage devices ho! updating is done on direct access and se"uential #grand $ather %ri&ary Storage Storage hierarchy pyra&id 'ey to disk and key to diskette
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ECHNOLOGY NOTES INFORMATION T ECHNOLOGY
Information Technology
organi ni)e )ed d co&* co&*in inat atio ionn and and use use o$ hard hard!a !are re++ so$t so$t! !are+ are+ Definition ( It is an orga tele teleco& co&&u &unic nicat atio ions ns++ data data*a *ase se &anag &anage& e&en entt and othe otherr in$o in$or& r&at atio ionn proc proces essi sing ng technologies used in a co&puter*ased in$or&ation syste&, In$or&ation technology trans$or&s data into a variety o$ use$ul in$or&ation products speci$ically *y the use o$ a co&puter, Com!t Com!ter er " It is a device that has the a*ility to accept data+ internally store and e-ec e-ecut utee a prog progra ra& & o$ inst instru ruct ctio ions ns++ per$ per$or or& & &ath &athe& e&at atic ical al++ logi logica call and and &anipulative operations on the data and reports on the results, %ut si&ply+ it is a &achin &achinee that that acc accepts epts data #input #input.. and proces processes ses it into into use$ul use$ul in$or& in$or&ati ation on #output., Com!ter Sy#tem It i# an interrelate$ #y#tem of in!t% roce##ing% o!t!t% #torage an$ control comonent# Thus a co&puter syste& consist o$ input and output devices+ pri&ary and storage devices+ the central processing unit+ the control unit !ithin the C%/ and other peripherals Data an$ Information concet# The The ter& ter&ss data data and in$o in$or& r&at atio ionn are loos loosely ely used used inte interch rchan angea gea*l *lyy in ordi ordina nary ry discu discuss ssio ions ns,, The The ter& ter&s+ s+ ho!e ho!ever ver++ are di$$ di$$ere erent nt in thei theirr usag usagee in the the $ield $ield o$ in$or&ation syste&s,
the co&p co&plet letee range range o$ $act $acts+ s+ events events++ trans transact actio ions ns++ and and opini opinion ons+ s+ Data Data & it is the 0udg&ents that e-ist *oth !ithin and outside the organi)ation, Data are ra! $acts $ro& !hich in$or&ation is produced, Information ( it is part o$ the total data availa*le !hich is appropriate to the re"uire&ents o$ a particular user or group o$ users, It is processed data upon !hich a user &ay rely $or decision,
A co&puter per$or&s the $ollo!ing *asic $unctions1 #a. Input ( co&puter co&puter accepts and captures data $ro& outside $or processing #*. %rocessing ( a co&puter per$or&s operations on data it holds #c. Storage ( a co&puter holds data *e$ore+ during and a$ter processing #d. Output ( a co&puter produces data $or use #in$or&ation. 2
ECHNOLOGY NOTES INFORMATION T ECHNOLOGY
Information Technology
organi ni)e )ed d co&* co&*in inat atio ionn and and use use o$ hard hard!a !are re++ so$t so$t! !are+ are+ Definition ( It is an orga tele teleco& co&&u &unic nicat atio ions ns++ data data*a *ase se &anag &anage& e&en entt and othe otherr in$o in$or& r&at atio ionn proc proces essi sing ng technologies used in a co&puter*ased in$or&ation syste&, In$or&ation technology trans$or&s data into a variety o$ use$ul in$or&ation products speci$ically *y the use o$ a co&puter, Com!t Com!ter er " It is a device that has the a*ility to accept data+ internally store and e-ec e-ecut utee a prog progra ra& & o$ inst instru ruct ctio ions ns++ per$ per$or or& & &ath &athe& e&at atic ical al++ logi logica call and and &anipulative operations on the data and reports on the results, %ut si&ply+ it is a &achin &achinee that that acc accepts epts data #input #input.. and proces processes ses it into into use$ul use$ul in$or& in$or&ati ation on #output., Com!ter Sy#tem It i# an interrelate$ #y#tem of in!t% roce##ing% o!t!t% #torage an$ control comonent# Thus a co&puter syste& consist o$ input and output devices+ pri&ary and storage devices+ the central processing unit+ the control unit !ithin the C%/ and other peripherals Data an$ Information concet# The The ter& ter&ss data data and in$o in$or& r&at atio ionn are loos loosely ely used used inte interch rchan angea gea*l *lyy in ordi ordina nary ry discu discuss ssio ions ns,, The The ter& ter&s+ s+ ho!e ho!ever ver++ are di$$ di$$ere erent nt in thei theirr usag usagee in the the $ield $ield o$ in$or&ation syste&s,
the co&p co&plet letee range range o$ $act $acts+ s+ events events++ trans transact actio ions ns++ and and opini opinion ons+ s+ Data Data & it is the 0udg&ents that e-ist *oth !ithin and outside the organi)ation, Data are ra! $acts $ro& !hich in$or&ation is produced, Information ( it is part o$ the total data availa*le !hich is appropriate to the re"uire&ents o$ a particular user or group o$ users, It is processed data upon !hich a user &ay rely $or decision,
A co&puter per$or&s the $ollo!ing *asic $unctions1 #a. Input ( co&puter co&puter accepts and captures data $ro& outside $or processing #*. %rocessing ( a co&puter per$or&s operations on data it holds #c. Storage ( a co&puter holds data *e$ore+ during and a$ter processing #d. Output ( a co&puter produces data $or use #in$or&ation. 2
COM'ONENTS AND CONFIG(RATION OF A COM'(TER
re$ers rs to the the phys physic ical al co&p co&pon onen ents ts o$ a co&p co&put uter er *oth *oth Com!ter Com!ter Har$)are Har$)are re$e &echanical and electronic, A co&puter is &ade up o$ the $ollo!ing co&ponents, Input devices Central %rocessing /nit Me&ory Secondary Storage unit Output devices
The con$iguration o$ a *asic co&puter syste&
IN'(T DE*ICES+METHODS These $acilitate co&&unication *et!een the user and the co&puter, They $acilitate the insertion o$ data into the co&puter $or processing,
#a. ,ey,e y-oa oar$ r$ A key*oard is laid out like a type!riter It allo!s data to *e typed in *y the pressing o$ the relevant keys The pressed key or instruction is displayed or e-ecuted This is the &ost co&&only used input device #Study 'eytodisk syste&s+ 'eytodiskette syste&s (Re$er to Cli$ton. #*. Mo!#e It is a hand held pointing device electronically connected to the co&puter !hich is used to control the cursor or a pointer on the screen through the rolling &otion o$ a *all on a $lat sur$ace, The cursor or pointer on the video screen &oves in the sa&e direction as the &ove&ent o$ the &ouse, 2hen the pointer is on the re"uired &enu ite& #icon. a *utton is clicked to select that ite&, 3
#c. Light 'en It is a penshaped device that uses photoelectric circuitry to enter data into the co&puter through a special video screen, A user can !rite on the video display ⇒ The high sensitive pen ena*les the co&puter to calculate the coordinates o$ the points on the screen touched *y the light pen The hand!riting or graphic is digitali)ed+ accepted as input and ⇒ displayed on the VD/ Input there$ore is directly onto the screen ⇒ #d. To!ch Screen# /se an inlaid screen to accept input through the act o$ physically touching the screen The co&puter senses the selected position and e-ecute the instruction accordingly This device !orks &ore suita*ly !ith &enu driven applications #e. Otical Character Rea$er# ⇒ These use photoelectric cells to &easure the a&ount o$ light re$lected $ro& a particular set o$ characters in a particular $ont ⇒ It then trans$ers the details to a co&puter ⇒ The reader incorporates a light *ea& !hich $ollo!s the outline o$ the characters *eing read ⇒ It co&pares these !ith stored re$erence characters The &ost co&&on $onts are OCRA #A&erican.and OCR3 #4uropean. ⇒ #$. Otical Mar. Rea$er# /OMR#0 These are si&ilar to OCRs *ut can detect &arks+ lines+ per$orations ⇒ rather than characters They !ork !ith speci$ic progra&s to read and interpret a particular ⇒ docu&ent #so are less $le-i*le than OCRs. OMRs are used to e-tract data $ro& surveys+ "uestionnaire $or&s or ⇒ &ark &ultiple choice e-a&s OMRs are also used in the processing o$ orders+ processing o$ ti&e ⇒ sheets $or !orkers+ inputting diagra&s into the co&puter, #g. Magnetic In. Character Rea$er# /MICR0 ⇒ They use preprinted hu&an reada*le characters ⇒ The characters are printed in a special ink &i-ed !ith iron o-ide ⇒ 3e$ore reading the docu&ent passes through a &agnetic $ield and the characters get &agneti)ed The &achine reader recogni)es the character *y its &agnetic $ield ⇒ pattern+ codes it and provides input into the co&puter, 4
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This ðod is not in general use *ecause the print has got to *e &ade in a special !ay to *e reada*le This ðod o$ input is !idely used in the *anking sector to process docu&ents like che"ues,
#h. 'age Scanner# These devices read docu&ents+ digitalise the& and sent the& $or ⇒ processing *y the co&puter These are like photocopying &achines that can read a !ide variety o$ ⇒ te-t and graphics including photographs, #i. 1ar Co$e Rea$er# 3ar coding is the representation o$ code nu&*ers or other data in the ⇒ $or& o$ optical or &agnetic *ars on a data carrier #*adge. !hich &ay *e tag+ la*el+ ticket+ plastic card A *ar code reader reads the *ar coding and allo!s the processing o$ ⇒ in$or&ation relating to the data The *ar code reader is usually hand held and uses a laser *ea& to ⇒ read, ⇒ 2hen a *ar code is read and recogni)ed+ the scanner e&its a short sound, ⇒ These are !idely used on *ank credit cards and in li*raries to identi$y *ooks and users
#0. 'oint of Sale /'OS0+Electronic 'oint of Sale /E'OS0 These are used in super&arkets ⇒ A %OS or 4%OS incorporates a scanner #*ar code reader.+ a printer ⇒ and a key*oard *uilt into a service point An ite& is passed through a !indo! through !hich the scanner can ⇒ see the *ar code and there*y identi$ies the ite&5 alternatively a hand held scanner is used to do the sa&e thing, ⇒ 2hen a *ar code is read and recogni)ed+ the scanner e&its a short sound, ⇒ The linked central co&puter then auto&atically looks up details relating to the ite&, ⇒ The details are then printed on the custo&er6s receipt #k. *oice Data Entry /*DE0 Can also *e called voice input or speech recognition ⇒ 5
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A voice recogni)ing device analyses and classi$ies speech or vocal tract patterns The device converts the speech into digital codes $or entry into the co&puter These are suita*le !here users do not !ish to use their hands to input data e,g, sorting o$ luggage at an airport+ recording o$ !eight in a slaughterhouse or *utchery, 7o!ever+ their use is li&ited *y the li&ited nature o$ recogni)a*le voca*ulary The co&puter needs to *e 8trained9 to recogni)e an individual6s voice, There are *ound to *e in accuracies in the data input so there is need $or a care$ul proo$ reading *y the user,
#l. *i$eo In!t Video i&ages can *e entered into the co&puter $ro& sources such as ⇒ a TV receiver+ VCR or ca&corder, ⇒ The data is digitali)ed and co&pressed $or storage on the co&puter6s &e&ory sites, ⇒ This ðod is used to input and store in$or&ation $or a *roadcaster o$ producer o$ optical disks Selection of the $ata collection metho$ /In!t $e2ice 3 metho$0 The $ollo!ing are the &ain $actors to *e considered !hen deciding on the data capture syste&s1 #a. Costs o$ the syste& ( costs &ust *e kept lo! #*. Accuracy ( should have detection and correction procedures $or errors #c. Ti&e ( turnaround ti&e in capturing data should *e short #d. Relia*ility ( The syste& o$ capture should *e $ree $ro& *reakdo!n #e. Fle-i*ility ( the syste& &ust cater $or di$$erent types o$ data #$. Volu&e ( a syste& should suit the volu&e o$ data to *e captured #g. 4-isting e"uip&ent ( a syste& that uses e-isting e"uip&ent !ould *e &ost pre$erred, #h. /ser $riendliness ( a syste& should render itsel$ easily to the user THE CENTRAL 'ROCESSING (NIT /C'(0 It is the unit o$ the co&puter syste& that includes the circuits that control the interpretation and e-ecution o$ instructions, It is the &ost i&portant co&ponent o$ a co&puter syste&, F!nction# of the roce##or To control the use o$ the &e&ory to store data and instructions 6
To control the se"uence o$ operations To give instructions to all parts o$ the co&puter to carry out processing The C%/ can *e su*divided into t!o &a0or su*units5 the control unit #C/. and the arith&etic logic unit #A:/., The pri&ary #&ain. &e&ory is an e-tension o$ the C%/ and assists the C%/ in its operations,
The Control (nit /C(0 It is the nerve center o$ the co&puter !hich controls and coordinates all hard!are operations i,e, those o$ peripheral units+ &ain &e&ory and the processor itsel$, It also controls the se"uence o$ the operations, The unit $etches #o*tains. the instruction $ro& the &ain &e&ory It then interprets it It then e-ecutes the instruction *y sending a co&&and signal to the appropriate hard!are device in the co&puter syste&+ ordering it to per$or& re"uired operations, The control unit is driven *y a ;clock pulse;5 the rate o$ the clock is called the speed,
The Arithmetic"Logic (nit /AL(0 This has t!o &a0or $unctions Carries out arith&etic tasks e,g, division+ addition etc %er$or&s logical operations e,g, co&paring data ite&s Ho) the AL( oerate#4 Data ite&s to *e processed are $etched $ro& the &ain &e&ory as directed *y the C/ into registers or accu&ulators !here they are stored, The A:/ then per$or&s the operations as directed *y the C/, The A:/ leaves the result in a data register $ro& !here they are placed into the &ain &e&ory again under the direction o$ the C/, The Main Memory It is an e-tension o$ the C%/ !hich gives i&&ediate access to data and progra&s, It is also called I&&ediate Access Me&ory #IAS., The &ain &e&ory holds three types o$ contents !hich are1 progra& instructions to *e e-ecuted or *eing e-ecuted Data to *e processed Results o$ processing
Operational $eatures
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The &e&ory has uni"uely a$$re##a-le #torage location# that are easily accessi*le to the C/, Rando& Access it is possi*le to $etch data $ro& the locations in &ain storage in any order and ti&e taken to access the location does not depend on the position o$ the location, Volatility the &ain &e&ory can *e volatile or nonvolatile depending on the its physical characteristics Details o$ single location 4ach location consists o$ tiny devices that can take t!o states #on
on., 4ach location in the &ain &e&ory holds a unit o$ data called a !ord, So&e co&puters had locations holding ? *inary digits and !ere there$ore said to have an ?*it !ord, Other co&puters have >@ *it storage locations+ !hile others tend to have B *it locations,
The Ran$om Acce## Memory /RAM0 This $or&s the largest part o$ the Main Me&ory and is o$ten used to &easure the po!er o$ a co&puter, It is used $or te&porary storage o$ data and progra&s during processing, RAM contains user data and application progra&s *eing processed, Data &ay *e rea$ $ro& RAM and data can also *e )ritten onto and stored on RAM, RAM contents are volatile i,e, stored data is lost and the contents disappear i$ the po!er is interrupted or !hen co&puter is s!itched o$$, Storage caacity on RAM The nu&*er o$ storage locations in RAM dictates the storage capacity or si)e o$ the co&puter, Storage on co&puter is "uoted in kilo*ytes #'*. or &ega*ytes #M*.
? *its >=B *ytes >=B E >=B *ytes >=B E >=B E >=B *ytes
> *yte > kilo*yte > &ega*yte > giga*yte
The Rea$ Only Memory /ROM0 It is used $or per&anent storage it holds the so$t!are progra&s such as operating syste&s+ interpreters and co&pilers, The progra&s are !ritten as part o$ the &anu$acturing process and the user cannot alter the&, ROM cannot *e !ritten on it only allo!s its contents to *e read, ROM contains data and instructions that the co&puter needs all the ti&e $ro& the &o&ent it is s!itched on, ROM contents are said to *e nonvolatile i,e, they do not disappear or get lost !hen the co&puter is s!itched o$$ or !hen po!er to the co&puter has *een interrupted,
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O(T'(T DE*ICES There are t!o $or&s o$ output devices+ those that produce hardcopy #per&anent. and those that produce so$tcopy, %rinters are hardcopy devices !hile the VD/ is a so$tcopy device, 7ardcopies are needed !hen copies are to *e taken a!ay $ro& the co&puter to *e sent to a user o$ the in$or&ation thereon+ or to *e $iled a!ay or even as legal docu&entation, Co&puters+ there$ore can produce a nu&*er o$ di$$erent docu&ent e,g, reports+ sales invoices+ payrolls+ or graphics, Tye# of 'rinter# %rinters can *e classi$ied in a nu&*er o$ !ays, #>. 3y print operation #a. Character printers #*. :ine printers #c. %age printers
#B. 3y ðod o$ producing print1 #a. I&pact printers #*. NonI&pact printers #. 3y speed o$ printing
#a. :o! speed printers #>=cps to ==lp&. #*. 7igh speed printers #over ==lp&.
The $ollo!ing is an illustration sho!ing the types o$ printers and their su* types and e-a&ples o$ these,
Co&puter %rinters
:ine %rinters
Character %rinters
%age %rinters
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Dru& Chain 4lectrostatic 4lectrostatic Magnetic Ion Deposition #3arrel. #Train 3and.
I&pact
Dot MatriInk 0et
:aser
NonI&pact
Daisy 2heel #%etal. Thi&*le
Ther&al
/a0 Line 'rinter# These produce a co&plete line o$ te-t in a single printing operation, These are suita*le $or *ulk printing, i, Dru& %rinters, • They e&ploy colu&ns o$ co&plete characters e&*ossed around the circu&$erence o$ a rapidly rotating dru&, • 4very print position is capa*le o$ *eing occupied *y any character • A print ha&&er situated at each print position $orces the paper against the dru& through the ri**on #interposed *et!een the paper and the ri**on. !hen the appropriate character is in position, • These are e-pensive to *uy and &aintain • The print "uality is poor #especially i$ there are &isti&ing o$ print ha&&ers. • They do not allo! $or change o$ $onts, • They are also very noisy
ii, •
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Chain #Train. %rinters They consist o$ a chain o$ characters &ounted on a chain that rotates in a hori)ontal plane, There is a ha&&er at each print position that strikes the appropriate character once it is in position, Character sets can *e easily changed *y replacing the chain, The principle o$ operation is si&ilar to that o$ dru& printers They are cheaper and $aster that dru& printers
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They produce *etter print "uality than dru& printers,
/-0 Character rinter# These are also kno!n as serial printers, These print one character at a ti&e across, The ðod o$ printing necessitates one #or t!o. print head#s., There are t!o categories o$ character printers1 imact and non"imact printers, Imact rinter# ( they $or& characters and graphics on the paper *y pressing a printing ele&ent #such as print !heel or cylinder. and an inked ri**on against paper e,g, a dot &atri- printer, Multiple copies can *e used through the use o$ a car*oni)ed paper, Non"imact rinter# do not use $orce and are "uieter than i&pact printers, They use specially treated paper and can $or& characters *y laser+ ther&al #heat. or electroche&ical processes, They produce higher "uality o$ print than i&pact printers, They+ ho!ever+ cannot produce &ultiple copies, They can print graphics and can support &any $onts, Tye# of Imact rinter#
#i. Dot Matri5 ( it consists o$ &atri- tiny tu*es containing needles in the print head, 4ach character in $or&ed $ro& the s"uare or rectangle array o$ dots, The needles are $ired onto the printer ri**on in a pattern corresponding to the shape o$ the character re"uired, 4ach character is printed *y the repeated hori)ontal &ove&ent o$ the print head, The "uality o$ the print depends on the dots in the &atri- #&ost co&&on are the ro!s *y G colu&ns &atrices., These printers are cheap to purchase and &aintain *ut do not produce good print "uality, #ii. Dai#y 6heel ( /ses a rotata*le !heel consisting a nu&*er o$ $le-i*le &etal or plastic spokes #usually G@. at the end o$ !hich is a &irror i&age o$ a character, During printing the !heel is rotated until the re"uired character co&es into line !ith the print ha&&er !hich then hits the character and the ri**on onto the paper and the paper is printed, They are cheap and o$$er *etter print "uality than Dot Matri%rinters, 7o!ever+ they are slo!er and &uch noisier, Tye# of Non"Imact 'rinter#
#i. Thermal rinter
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The print head o$ a ther&al printer contains an array o$ heating ele&ents that have electric currents s!itched through the& so as to $or& the re"uired character, 2hen the print head co&es into contact !ith a special paper+ it *urns a!ay an alu&inu& coating to reveal a *lack core, They can produce colour printing and can produce high "uality prints, 7o!ever+ they use only a special type o$ paper,
#ii. In. & 7et 'rinter# These spray dots o$ ink to $or& characters under electronic control, These are "uieter and produce higher print "uality even graphics5 they can print in colour and can print &any $ont types and si)es, 7o!ever they are &ore e-pensive to purchase and &aintain,
#c. 'age 'rinter# They print one co&plete page at any given ti&e, Although they appear to produce a co&plete page+ they actually produce the docu&ent *y printing a line at a ti&e *ut their speed o$ operation is such that the $ull e$$ect is that o$ creating the !hole page,
Tye# of age rinter#
#i. La#er 'rinter# They $or& characters *y $lashing a lo!po!ered *ea& onto a rotating dru&, A special ink #toner. is then attracted to the lasere-posed areas o$ the dru&, The docu&ent;s outline are created *y $lashing a photographic negative o$ the docu&ent onto the photoconductive dru&, The co&plete photoconductive dru& sur$ace stores the resulting i&age, 2hen the paper co&es into contact !ith the dru& the i&age is then trans$erred and then $used per&anently onto it, The photo conductive dru& is erased *e$ore receiving the ne-t i&age these operation occur !hile printing is in progress, They can print an in$inite nu&*er o$ $onts and can even &i- di$$erent $onts in the sa&e line, They can produce high "uality print+ and can *e used to print logos+ illustrations and graphics, They are very "uiet during printing, 7o!ever+ they are very e-pensive to purchase and &aintain, #ii. Magnetic 'rinter#
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They use a rotating dru& or *elt onto !hich tiny &agnetic dots are recorded, The i&age $or&ed is coated !ith toner against !hich heated paper is pressed to $or& the re"uired i&age on paper, Typical printer speeds %rinter Type Fonts Speed Daisy 2heel Dot &atriInk 0et Dru& Chain Magnetic :aser #s&all. :aser #large.
I&pact I&pact Noni&pact I&pact I&pact Noni&pact NonI&pact Noni&pact
Many Many Any Fi-ed Many Any Any Any
B===cp& >H===cp& >H===cp& BH==lp& B===lp& H===lp& >=pp& H==pp&
Factors in$luencing the choice o$ a printer The cost o$ the printer %urpose o$ the output The volu&e o$ !ork to *e printed The environ&ent in !hich the printer !ill !ork Nature and desired "uality o$ the docu&ent#s. to *e produced
Other Form# of Com!ter O!t!t Seech O!t!t /So!n$ O!t!t0 So&e co&puters are capa*le o$ producing speech, The co&puter can actually speak out $ro& a stored digital representation o$ either !ords or other sounds, A person;s voice can *e stored and reproduced later, This ðod o$ output is o$ great use to the *lind+ or in poor light, Advanced $or&s o$ speech output are *eing used to ans!er telephones+ ans!er so&e in"uiries $ro& an organi)ation;s callers etc, SECONDARY STORAGE DE*ICES This is also called *acking storage or au-iliary storage, It is used to supple&ent the co&puter;s &ain &e&ory, Main &e&ory is volatile and e-pensive+ there$ore *acking storage is used to hold progra&s and data $iles !hen they are not re"uired in the &ain &e&ory, The speed o$ accessing *acking store is &uch slo!er than that $or accessing in IAS, 1ac.ing Store De2ice# Floy Di#. Dri2e These !ork in con0unction !ith $loppy or &agnetic diskettes, They have a narro! slot !here the diskette is inserted, The slot has a push *utton or
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lever !hich &ust *e closed !hen the diskette has *een inserted, The process o$ closing engages a turn ta*le !hich rotates the disk and so *rings the read. Most disks are ,Hinch and capacities o$ >,M*
Caring for $i#.ette# /se !rite protect security tag to prevent accidental erasure o$ data %rotect the disk $ro& dust+ rain+ hu&idity+ store in an envelop Do not *end the disk Do not touch the recording sur$ace Store diskette in a te&perature o$ >= ° C to HB° C Do not place the diskette in a &agnetic $ield Har$ Di#. They are per&anent $i-ed hard disks !ith lu*ricated sur$aces to allo! read*. They have $aster data trans$er rate and are relia*le, 7o!ever+ they need very care$ul security procedures Modern co&puters #note *ooks. have re&ova*le disk cartridge versions, Magnetic Tae This is si&ilar to the kind $ound $or audio or video tapes It is a $il& coated !ith iron o-ide %ortions o$ the tape are &agneti)ed to represent *its It uses separate read !rite heads to trans$er data $ro& the tape to the &ain &e&ory and to record, Vacuu& colu&ns in the unit a*sor* the $orce o$ sudden starts and stops to prevent tape snatches, 14
They store data in a se"uence so data has to *e &oved over se"uentially in order to read the re"uired+ this &eans access is slo!er,
Feat!re# of the Magnetic Tae - Co&&on !idth o$ >,Bc& and length o$ >==& to >>==& - Data is stored on tracks !hich run along the tape - The *eginning and end o$ the tape are &arked *y an alu&inu& strip - Recording densities range $ro& B== to @=== *ytes per inch #*pi. - 7as storage capacity o$ B=M* to >@=M* - The tape is reusa*le to prevent accidental erasure+ a !rite per&it ring is attached !hen !riting is re"uired, The E5changea-le Di#. (nit /Magnetic Di#.0 They are coated !ith iron o-ide They can *e steel platters #hard disks. or plastic #Floppy. 4ach disk is divided into B== concentric tracks or rings Data is recorded on the track *y &oving a read> disks that are insepara*le, The disk pack is $itted into a unit or drive !hich has a co&*type asse&*ly containing one read+ representing the presence o$ a crevice, So the presence or lack o$ a crevice deter&ines the *it, The disk cannot *e erased or over!ritten+ this $eature is kno!n as 2ORM #!rite once read &any ti&es. 15
Thus the disk is called CDROM #Co&pact disk read only Me&ory., They have great storage capacities o$ H=M* to >=*, Access to stored data is very $ast They can *e used to store te-t+ graphical+ audio or video data They are suita*le $or storing large a&ounts o$ data, 7o!ever+ they can not *e edited
COM'(TER SYSTEMS Co&puters can *e classi$ied as general purpose or special purpose, eneralpurpose co&puters are used to per$or& a variety o$ applications and the &ost co&&on in *usiness !hile special purpose co&puters are used $or speci$ic or li&ited applications e,g, &ilitary or scienti$ic research, Co&puters can *e classi$ied *y #i8e or *y !#e Categories o$ Co&puter Syste&s #*y si)e. #i. Microco&puters #ii. Minico&puters #iii. Main$ra&e co&puters #iv. Super co&puters Microcom!ter# They are also called %ersonal Co&puters #%Cs. or Desktop Co&puters, These are relatively s&all and ine-pensive, They consist o$ a single processor or a chip The syste& is nor&ally &ade up o$ the &icroprocessor+ key*oard+ VD/ one or t!o $loppy disk drives+ a printer and a hard disk drive, It has a hard disk capacity o$ B=M* to HB=M* May use a colour or &onochro&e cathode ray tu*e #CRT. 7ave capa*ilities $or net!orking, They are single user, They occupy little space, They are capa*le o$ &ultiprogra&&ing, They are co&pati*le !ith a !ide range o$ so$t!are, %Cs co&e in a variety o$ si)es1 note*ooks #handheld.+ laptops+ desktops and $loor standing,
Minicom!ter Sy#tem /Mi$"range Com!ter#0 They are syste&s the si)e o$ a s&all ta*le that can acco&&odate a nu&*er o$ users at a ti&e, They have storage capa*ility larger than personal co&puters, They can support a variety o$ transaction processing activities 16
Har$)are feat!re# - Support &agnetic tape storage - They are &ultiuser &ore than >== users at ti&e $or super &inis - 7ave &ultiple hard disks+ *oth $i-ed and e-changea*le - Can *e upgraded !hen necessary - They do not re"uire a special environ&ent to !ork so can allo! $or decentralisation, - They are less e-pensive than the &ain$ra&e syste&s - They have *igger capacities than &icroprocessors+ so&e have B *it &icroprocessors, Mainframe com!ter# These are large+ po!er$ul co&puters !ith a lot o$ processing capa*ilities, They are suita*le $or &ediu&si)e to large corporations, They can also *e linked together to $or& a po!er$ul and $le-i*le syste&, Har$)are Feat!re# - Si&ilar to &inico&puters *ut have several large processors and high processing speeds o$ up to B== &illion instructions per second #&ips. - They have &assive a&ounts o$ storage po!er, - They can use high speed line printers - They have a large nu&*er o$ &agnetic disks and tape units !ith large capa*ilities - They are &ultiuser and &ulti processing - They have i&proved relia*ility - Their per$or&ance &ay *e enhanced *y slotting a s&aller syste&+ like a &inico&puter *et!een the ter&inal and the &ain processor the $ront end processor #F4%. - 3oth processors run concurrently !ith the F4% passing on partially processed data to the &ain $ra&e $or $urther processing, - They+ ho!ever+ are e-pensive to *uy and &aintain+ they need special and very e-pensive so$t!are and they also re"uire a special environ&ent, - They can *e used $or large corporations #such as large international *anks. and govern&ent depart&ents S!ercom!ter Sy#tem# These are e-tre&ely po!er$ul &ain$ra&e co&puter syste&s, They are speci$ically designed $or highspeed nu&eric calculations, These an process hundreds o$ &illions instructions per second #&ips. They can *e used *y govern&ent research agencies+ national !eather $orecasting+ spacecra$t construction and navigation, 17
Con#i$eration# on cla##ification# -a#e$ on #i8e
The classi$ication o$ co&puters *ased on the physical si)e o$ the co&puter has *eco&e *lurred and a *it &isleading, So&e see&ingly s&all syste&s can per$or& &ore po!er$ully than the larger ones, The po!er o$ the co&puter syste& depends on the &icroprocessor , A &icroprocessor is a type o$ an integrated circuit #ic., It has t!o distinct characteristics !ord si)e and speed o$ operation, 2ord si)e the nu&*er o$ *its dealt !ith at the sa&e ti&e+ so&e processors are ? *it+ others even B *it, The larger the !ord si)e the &ore po!er$ul a co&puter syste& is, So so&e physically *igger syste&s &ay have s&aller !ord si)es and hence less po!er, Speed o$ the &icroprocessor it is the clock rate or rate o$ data trans$er+ it is the rate at !hich data *its are &oved around inside at *its per second #&egahert). this is also called the *aud rate, Syste&s !ith higher speeds tend to *e &ore po!er$ul though they tend to *e physically s&all,
Com!ter cla##ification -y !#e >, The 6or$ 'roce##or " it is a co&puter used to produce o$$ice docu&ents usually in te-t, It has very li&ited &e&ory and processing capa*ilities, They are cheap to *uy B, Home Com!ter " it is a cheap co&puter that is used $or do&estic purposes e,g, progra&&es $or ga&es and controlling ho&e $inances, , 'er#onal Com!ter " it is a &icroco&puter that is usually $or use *y one person in an o$$ice or at ho&e, , De#.to " any co&puter designed to *e used on a desk in an o$$ice environ&ent H, 6or.#tation " a co&puter ter&inal #%C or desktop. designed to support the !ork o$ one person, It can *e highpo!ered or have other superior capa*ilities to %Cs or ordinary desktops e,g, capacity to do calculations+ graphics and other advanced logical operations,
@,
,
La " to " it is a s&all co&puter !ith a $lat screen that a user can place on his lap, It is porta*le and has an in*uilt rechargea*le *attery that can support it !hen there is no po!er $ro& the &ains, It can *e carried in a *rie$case, Em-e$$e$ Com!ter# " These are co&puters in other devices that cannot *e accessed directly e,g, those in petrol pu&ps+ ATMs+ vending &achines+ cellphones and elevators,
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SOFT6ARE Soft)are re$ers to co&puter progra&s that control the !orkings o$ the co&puter hard!are+ along !ith the progra& docu&entation used to e-plain the progra&s to the user, Com!ter rogram# are sets o$ instructions or state&ents to the co&puter that direct the circuitry !ithin the hard!are to operate in a certain $ashion, So$t!are can *e classi$ied into
Three di$$erent categories are >, Syste&s So$t!are B, Application So$t!are , Develop&ent So$t!are SYSTEMS SOFT6ARE It is a collection o$ progra&s that interact !ith the co&puter hard!are and application so$t!are progra&s creating a layer o$ insulation *et!een the t!o, Syste&s So$t!are contains instructions !hich1 #a. Manage a co&puter syste&6s hard!are co&ponents to coordinate the& so that they !ork e$$iciently #*. Schedule the co&puter6s ti&e to &ake the *est use o$ that ti&e,
Syste&s So$t!are includes a variety o$ progra&&es such as1 #i. Operating Syste&s #ii. Data*ase Manage&ent Syste&s #iii. Co&&unications Control %rogra&s #iv. Service and /tility %rogra&s #v. %rogra&&ing :anguage Translators Oerating Sy#tem# This $or&s the largest co&ponent o$ Syste&s So$t!are, ⇒ It is a syste& o$ progra&s that run or control the e-ecution o$ co&puter progra&s and act as an inter$ace !ith application progra&s, ⇒ It is an integrated syste& o$ progra&s that &anages the operations o$ the C%/+ controls the input, Output and storage resources and activities o$ a co&puter syste&, ⇒ The pri&ary purpose o$ the operating syste& is to &a-i&ise the productivity o$ a co&puter syste&, It &ini&ises the a&ount o$ user intervention re"uired during data entry and processing, It helps application progra&s per$or& co&&on
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operations such as entering data+ saving+ retrieving $iles+ printing and displaying output, F!nction# of an Oerating Sy#tem enerally the operating syste& is e-pected to per$or& $ive *asic $unctions
#a. (#er Interfacing ( an Operating Syste& allo!s a user to co&&unicate !ith the co&puter in loading progra&s+ accessing $iles and acco&plishing tasks through co&&and driven+ &enu driven or graphical user inter$aces, In co&&and driven inter$aces+ the user uses *rie$ end co&&ands+ in &enu driven inter$aces the user selects choices $ro& &enus o$ options+ in graphical user inter$ace #/I. the user selects icons+ *ars+ *uttons+ *o-es or other i&ages to hi& get things done *y the syste&,
#*. Oerating En2ironment Management ( /se o$ /I ena*les the user to connect to other separate application packages so that they can co&&unicate and !ork together and share data $iles, Operating environ&ent packages provide icon displays and support the use o$ so&e input devices to allo! the running and output o$ several progra&s to *e displayed at the sa&e ti&e, The Operating Syste& allo!s $or &ultitasking ( i,e, !here several progra&s or tasks can *e processed at the sa&e ti&e, #c. Re#o!rce Management ( Resource &anage&ent progra&s o$ the operating syste& &anage the hard!are resources o$ a co&puter syste& including the C%/+ &e&ory+ secondary storage devices and input
#e. Ta#. Management ( The task &anage&ent progra&s o$ an operating syste& &anage the acco&plish&ent o$ co&puting tasks as needed *y the user, They 20
give each task a slice o$ the C%/6s ti&e and interrupt the C%/ operations to su*stitute other tasks, Task &anage&ent &ay involve m!ltita#.ing ( !here several co&puting tasks can occur at the sa&e ti&e, Multitasking &ay *e in the $or& o$ m!ltirogramming #several progra&s are running at the sa&e ti&e., The operating syste& allo!s $or ti&e sharing ( !here the co&puting tasks o$ several users can *e processed at the sa&e ti&e, Multitasking depends on the co&puting po!er o$ the C%/ i$ too &any progra&s are running concurrently the syste& &ay *e overloaded or processing slo!ed do!n, 4-a&ple o$ &ultitasking1 printing and typing at the sa&e ti&e+ !ord processing and $inancial analysis+ *ro!sing the internet and !ord processing, 'o!lar Oerating Sy#tem# MS"DOS /Micro#oft Di#. Oerating Sy#tem0 It has *een !idely in use especially *e$ore >GGH !hen the ne! 2indo!s GH took ⇒ over, ⇒ It is a single user operating syste& ( only one user can *e using the syste& at a given ti&e, ⇒ It is a single tasking operating syste& ( It allo!s $or the processing o$ only one task at a ti&e ⇒ /se o$ short pro&pt co&&ands ( the user inter$aces !ith the co&puter syste& through the use o$ co&&ands that are $ed into the co&puter usually a$ter the pro&pt sign #J. e,g, C1KJcls #Co&&and to clear the screen. ⇒ Instructions are put in only through the key*oard Once a $ile is deleted it can never *e recalled ⇒ The operating syste& is not user$riendly ⇒ 6in$o)# A !ido!s *ased operating syste& is &ore advanced than the MSDOS *ased ⇒ operating syste&, It $eatures graphical user inter$aces #/Is. ( /ser can $eed co&&ands into the ⇒ co&puter through the selection o$ relevant icons+ *ars+ *uttons+ *o-es or other $or&s o$ i&ages #&ostly rese&*ling the intended device or operation., ⇒ True &ultitasking ( the operating syste& allo!s $or nu&erous tasks to *e done at the sa&e ti&e, ⇒ Net!orking ( the operating syste& is &ultiusa*le ( &any users can use it at the sa&e ti&e, It is capa*le o$ holding a nu&*er o$ co&puter syste&s net!orked together, Multi&edia %resentations the operating syste& allo!s $or the presentation o$ ⇒ in$or&ation in a variety o$ &edia including te-t+ graphic displays+ voice and other audio+ photographs and video, 21
Virtual Me&ory ( It allo!s $or the use o$ storage devices as e-tension o$ the &ain &e&ory thus giving the appearance o$ a larger &ain &e&ory than actually e-ists, ⇒ Deleted $ile go to recycle *in ⇒ Makes use o$ easier input ðods e,g, &ouse+ 0oystick ⇒ 2indo!s operating syste&s has MSDOS option ⇒ 4-a&ples o$ 2indo!s Operating Syste&s packages+ 2indo!s NT #ne! technology. #>GG. and 2indo!s GH, ⇒ In co&puter ter&s+ a !indo! is one section o$ a co&puter6s &ultiple section display screen that can have a di$$erent display, OSGG !ith the ⇒ OS
The Macinto#h Sy#tem It is an operating syste& $or Apple $ro& Macintosh &icroco&puters ⇒ It is a popular /I as !ell as &ultitasking and virtual &e&ory operating syste&, ⇒ It is &ade up o$ the $ollo!ing progra&s1 :anguage translators /tility progra&s Control progra&s Co&&unication progra&s Lang!age tran#lator# an$ (tility rogram#
Non&achine languages &ust *e converted into &achine language to *e e-ecuted *y the C%/, This is one *y syste&s so$t!are called language translators, A lang!age tran#lator converts a state&ent $ro& a highlevel progra&&ing language into &achine language called source code !hereas the &achine language code is re$ereed to as the o*0ect code, The translator converts the co&&and given in hu&an language into the $or& the co&puter has *een progra&&ed to understand *e$ore e-ecuting the instruction, There are t!o types o$ language translators ( Interpreter L Co&piler 22
Interreter This is a language translator that converts each #tatement in a progra& into &achine language and e-ecutes the progra&&e state&ent at a ti&e Comiler This This languag languagee transl translato atorr transl translates ates a comlete rogram into a co&plete &achine language progra&, The result is a progra& in &achine language that can *e run in its entiret entirety+ y+ !ith !ith a co&pil co&piler+ er+ progra& progra& e-ecution e-ecution is a t!os t!ostag tagee process process,, First+ First+ the co&piler translates the progra& into a &achine language5 second the &achine language progra& is e-ecuted, Co&pilers run $aster than interpreters so are &ore pre$erred, (tility rogram# It is a standard standard set o$ routines routines that assist the operation operation o$ the co&puter co&puter syste& *y per$or&ing so&e $re"uently re"uired processes such as to sort and &erge sets o$ data+ copy and keep track o$ co&puter 0o*s *eing run, Control rogram# These are designed to &anage the general $unctions o$ the processor+ &e&ory and ter&inal inter$ace, The progra&s are arranged in a hierarchy at the top o$ !hich is a that controls the running o$ the other progra&s, In .ernel or e5ec!ti2e rogram that &icroco&put &icroco&puters ers the supervisor supervisor is held in ROM !hile on larger co&puter co&puter syste&s it is held on *acking store, 2hen the co&puter is s!itched on the supervisor is loaded into &ain &e&ory+ the other progra&s are kept on disk and are trans$erred to &ain &e&ory !hen they are needed, The kernel assists the $ollo!ing1
The 9o- #che$!ler selects+ initiates+ ter&inates+ "ueues and se"uences the 0o*s that de&and the use o$ the processor and &ain &e&ory, The file manager has the responsi*ility o$ achieving the interleaving e$$ect o$ Multiprogra&&ing, The In!t+O!t!t manager has the responsi*ility o$ &anaging the inter$ace !ith ter&inals and *acking store in response to the re"uire&ents o$ any applications progra& *eing e-ecuted, Comm!nication# Comm!nication# 'rogram#
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These support net!ork co&puter syste&s *y allo!ing di$$erent types o$ hard!are to *e linked and to co&&unicate !ith each other, The progra&s &ay help to select the *est trans&ission &ediu& $or the &essage+ coding and sending the data, *irt!al Storage Oerating Sy#tem
This re$ers to a syste& $or e-tending the capacity capacity o$ &ain &e&ory $or running large applic applicati ation on or utilit utilityy progra progra&s, &s, The operat operating ing syste& syste& separa separates tes progra progra&s &s into into sections sections so&e o$ !hich !hich are put into *acking store, The locations locations o$ these sections sections #addresses. and the part o$ the progra& *eing e-ecuted e-ecuted are held in &ain &e&ory5 the sections are called in and processed 2hen re"uired re"uired and then returned returned to *acking *acking storage, The sections o$ the progra&s progra&s are called pages pages and are said to page in $ro& *acking *acking store and page out !hen *eing replaced *y other pages, The e-ecution o$ virtual storage is there$ore called paging,
A''LICATION SOFT6ARE Applications are progra&s designed to help the user carry out speci$ic tasks $or ⇒ e-a&ple to &anipulate $igures or !rite te-ts, This This also lso cons consiists sts o$ progr rogra& a&ss !rit ritten ten to solv solvee artic!lar !#er"oriente$ ⇒ ro-lem#: It applies the po!er o$ the co&puter to give individuals+ groups and organisations the a*ility to solve pro*le&s and per$or& speci$ic activities or tasks e,g, Accounts receiva*le+ accounts paya*le+ auto&atic teller &achines+ inventory control+ li*rary operations and Control+ invoicing etc Categories o$ generic applications1 6or$ 'roce##ing A !ord processing package is designed to ena*le te-t to *e typed and &anipulated, ⇒ It has &any advantages over the type !riter+ ⇒ the a*il a*ilit ityy to edit edit part partss o$ the the te-t te-t !ith !ithou outt re!r re!rit itin ingg the the !hol !holee - the docu&ent allo! !s $or $or spell checking - allo checking $or& the co&puter;s Dictionary File+ i$ it assu&es a !ord is &isspelt i$ not $ound in the dictionary. it highlights it or so&eti&es even correct it auto&atically, allo!s $or centering centering te-t+ -ol$ - allo!s -ol$%% underline and use o$ variety o$ $onts #type$aces. - allo!s $or the production o$ &ultiple original copies $ro& one so$tcopy, ⇒ %opular 2ordprocessing packages are Microso$t 2ord+ :otus 2ord+ 2ord%er$ect+ uattro 2ord, Srea$ #heet#
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A spreadsheet package is used to per$or& calculations that have *een entered onto a grid, For&ulae are entered into the grid using the $igures+ i$ the $igures change5 the results o$ the $or&ulae are updated auto&atically, It is also possi*le to $ilter #select only the re"uired data.+ sort or per$or& other $or&s o$ data &anipulations, It is possi*le to produce graphs+ charts and other $or&s o$ co&parison using the entered $igures $ro& the spreadsheet, %opular e-a&ples o$ spreadsheet packages are1 Microso$t 4-cel+ :otus >B+ uattro %ro
Data-a#e# - A data*ase is an organised store o$ in$or&ation+ $or e-a&ple an address *ook+ list o$ e&ployees+ list o$ students+ custo&ers or ite&s o$ assets, - A data*ase package is used to store records, - Data can *e sorted+ $iltered $or separate vie!ing, - Calculations and co&parisons *et!een data ite&s can *e done, - %opular data*ase packages are1 Microso$t 4-cel+ lotus Approach+ %arado-+ d3ase IV+ Data 4ase, Grahic# - Thes Thesee are are appl applic icat atio ions ns desig esigne ned d sole solely ly $or $or desi design gnin ingg gra graphs phs and and te-t te-t charts
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S!ite# " Many applications are grouped together into suites !hich users can purchase as one product containing+ $or e-a&ple+ 2ord%rocessing+ a Spreadsheet+ raphics application+ Desktop %u*lishing+ Data*ase application, The follo)ing i# the criteria for #electing alication# #oft)are4 Accuracy it &ust *e $ree $ro& errors Fle-i*ility &ust *e a*le to adapt to changing environ&ent, Co&pati*ility it &ust *e co&pati*le !ith availa*le hard!are Recency it &ust *e current Cost it &ust have reasona*le cost Originality It &ust *e original Support consider continued support $ro& the supplier, 4ase o$ use it &ust *e user $riendly, %er$or&ance it &ust have e$$iciency in *oth response ti&e and run ti&e, So!rce# of Alication# Soft)are There are three sources o$ applications so$t!are5 Inhouse O$$the shel$ Fro& a contractor, In"ho!#e De2eloe$ Soft)are This approach re"uires a develop&ent tea& $ro& !ithin the organisation, The tea& is usually co&prised o$ progra&&ers and analysts, The tea& &e&*ers should *e high cali*re+ highly trained and relia*le A$2antage# Internal pro$essionals understand operations *etter and there$ore can produce an ⇒ accurate solution, The So$t!are usually &eets user re"uire&ents, ⇒ Manage&ent are in total control o$ the develop&ent process ⇒ More $le-i*ility there is &ore $le-i*ility in &aking &odi$ications, ⇒ %ro*le& speci$icity inhouse developed so$t!are can give an organisation ⇒ so$t!are progra&s that are easily tailored to a uni"ue pro*le& or task, Di#a$2antage# ⇒ Ti&e and costs o$ developing the progra& &ay *e greater than other options ⇒ Inhouse sta$$ &ay lack the e-pertise needed $or the pro0ect ⇒ Relia*ility o$ the resultant so$t!are is highly "uestiona*le, In so&e cases the developers &ay atte&pt to gain $raudulently $ro& the syste& ⇒
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Off"the Shelf This is so$t!are that can *e purchased+ leased+ or rented $ro& a so$t!are co&pany that develops progra&s and sells the& to &any co&puter users and organisations, Applications such as $inancial accounting+ *usiness graphics and pay roll &ay *e *ought, A$2antage# ⇒ Cheaper the so$t!are co&pany is a*le to spread the so$t!are develop&ent cost over a large nu&*er o$ custo&ers+ hence reducing the cost any one custo&er &ust pay, :ess risky the so$t!are is e-isting+ hence you can analyse the $eatures and ⇒ per$or&ance o$ the package, The progra& is a !elltried and tested product !ith $e! errors, ⇒ :ess ti&e O$$the shel$ so$t!are is o$ten installed "uickly and easily, ⇒ The package is !ell docu&ented ⇒ The packages re"uire little &aintenance ⇒ ⇒ There is continued support $ro& the supplier through upgrades, Di#a$2antage# ⇒ The organisation &ight need to pay $or the $eatures that are not re"uired and never used, ⇒ Tie package &ay *e $or general needs and there$ore not ideal $or the user, The user has no direct control over the package+ ⇒ So$t!are $ro& a Contractor This involves contracting out so$t!are develop&ent to a so$t!are house *etter kno!n as outsourcing especially !here o$$theshel$ packages are not availa*le, A$2antage# So$t!are houses e&ploy pro$essionals and this &ay *ene$it the organisation ⇒ Trans$er o$ skills to the e-isting pro$essionals in an organisation ⇒ Organisation can get support $ro& the contractor, ⇒ Di#a$2antage# ⇒ There could *e *reach o$ con$identiality, ⇒ Contractor &ay go *ankrupt and cease trading leaving the user !ith no support, ⇒ Contractor &ight not have su$$icient e-perience or understanding o$ the pro*le& thus the solution &ight not *e satis$actory, ⇒ It takes ti&e $or the contractor to understand the user;s *usiness and operations this &akes the approach e-pensive, DATA COMM(NICATION 27
Re$ers to the &eans and ðods !here*y data is trans$erred *et!een processing locations through the use o$ co&&unication syste&s, Comm!nication #y#tem# are de$ined as syste&s $or creating+ delivering+ and receiving electronic &essages, The co&&unication syste& co&prises o$ the $ollo!ing1 a device to send the &essage - The channel or co&&unication &ediu& - A device to receive the &essage - A device to send the &essage Mo$e# of Comm!nication an$ Co$e# There are various &odes and codes o$ data trans&ission signals $ro& the sending to the receiving device, Analog!e tran#mi##ion Analogue signals are continuous sine !aves that send a continuous Hvolt signal on a channel *ut the signal !ill vary continuously *et!een H to H volts, The nu&*er o$ cycles per second is the $re"uency o$ the signal and is e-pressed in units called hert) #7)., The hu&an voice $or&s oscillating patterns o$ changes in air pressure, The vi*rations act on the telephone &icrophone and are converted to electrical voltage patterns that re$lect the characteristics o$ the speech pattern, Analogue trans&ission is used to trans&it voice or data in analogue signals, It is used in telephone syste&s and radio trans&ission,
Voltage Analogue Signal H
H
Ti&e
Digital Tran#mi##ion This is the sending o$ data !ith digital sy&*ols o$ = and > representing the s!itching on #>. and s!itching o$$ #=. pulses o$ electricity, Most co&puter syste&s use this to create *its that &ake up *ytes, One cycle is &ade up o$ t!o pulses, The nu&*er o$ pulses per second is called the *aud rate, Digital Signal
1
1
1 0
0
0
28
Time
Digital Trans&ission Versus Analogue Trans&ission Digital trans&ission o$$ers less errors and noise in trans&ission especially over long distances, There is little data $atigue as the data *eing send does not lose po!er over the trans&ission so &uch that the signal is !eakened *y the length o$ the trans&ission &edia, Digital trans&ission is co&pati*le !ith digital co&puters so there is no need to convert the data &essages $ro& analogue to digital !hen co&puter syste&s are using digital trans&ission lines, 7o!ever+ the setting up o$ digital trans&ission lines especially over long distances is considera*ly e-pensive, Data Tran#mi##ion Mo$e# These are !ays through !hich organisations can co&&unicate via the channel or trans&ission &edia, Simle5 tran#mi##ion Trans&ission takes place only in one direction, These are not suita*le $or long distance trans&ission *ecause there is need $or ackno!ledge&ent or error &essages, It is used in the co&puter printer co&&unication, This is also used in radio and television trans&ission, Sender
Receiver
Half D!le5 Messages can *e sent *oth !ays *ut only one !ay at a ti&e, The channel alternately sends and receives data *ut these are not done at the sa&e ti&e, The sa&e device is used $or *oth sending and receiving, This is used in t!o!ay radio co&&unication, Sender
Receiver
F!ll D!le5 This per&its si&ultaneous trans&ission o$ &essages in *oth directions, Sending and receiving can *e done at the sa&e ti&e using the sa&e devices, This is the &ode used in &odern telephone
Receiver
29
6ay# of Tran#mitting Data a, A#ynchrono!# Tran#mi##ion 4ach character is sent do!n the channel separately that each trans&ission unit is one unit in length, The characters are sent character *y character at irregular intervals, The character is headed *y a start *it and ended *y a stop *it, These *its tell the receiving device that a character is co&ing and that the character has *een sent, There &ay *e a parity *it to veri$y correctness o$ trans&ission, 4ven parity is used !here the nu&*er o$ *its in the character is even and an odd parity syste& $or the character !ith an odd nu&*er o$ *its, This $or& is suita*le conversational interactions and used in standard telephone lines using lo! trans&ission rates, Synchrono!# tran#mi##ion %repared sets o$ characters are trans&itted together as *locks at $i-ed rates, The &essage is preceded *y the parity *its to veri$y !hat has *een received, The *eginning and end *its represent s&all percentages o$ the total *its sent thus reducing overhead costs o$ co&&unication, Synchronous Trans&ission is $aster and less e-pensive as given in that character are *locked and sent do!n as one &essage allo!ing $or the trans&ission o$ a $uller &essage, 'rotocol# There is need $or there to *e a !ay o$ signalling the start and end o$ the
&essage *y the use o$ data trans&ission protocols, The use o$ the parity *its is one ðod+ use o$ roger+ over are protocols in t!o!ay radio co&&unication, S)itching Alternati2e#
Circuit S!itching 2hen a call is &ade the co&&unication channel is opened and kept open until the co&&unication session is co&plete, Message S!itching 4ach &essage is sent to the receiver i$ a route is availa*le, The &essages are sent in *locks one at a ti&e, The &essage &ay *e stored $or later trans&ission i$ the route is not availa*le+ so&eti&es this is called storeand$or!ard trans&ission, The &essage is delivered !hen the route *eco&es availa*le or upon de&and $ro& the receiver,
30
%acket S!itching This involves su*dividing the &essage into groups called packets, 4ach packet is then sent to the destination separately via the $astest route, At the destination the packets are put in se"uential order and delivered to the receiver, So&eti&es !hen there is no route open+ the packets are stored and then $or!arded once the route is open+ so these are also storeand$or!ard syste&s , These $ully put the net!ork to *etter utilisation, Comm!nication Channel# So!rce# an$ Me$ia
a, Telehone Sy#tem# telephone lines are used !ith online syste&s, The lines can *e divided into leased and dial service lines, #i. :eased :ines These are telephone lines that are dedicated to the sole use *y the user to support online syste&s !ithin the organisation, The telephone service provider #e,g Tel One. then charges a $lat &onthly rate $or the service, In calculating the rate the length o$ the line &ay *e considered, #ii. Dial service 2ith this telephone line the user is charged each ti&e the line is used $or online processing, 2hen all the lines connecting the syste& are *usy a user has to !ait and an appropriate &essage is given *y the syste&, The rate charged depends on the distance+ ti&e o$ use #peak or o$$ peak.+ ti&e spent during trans&ission, This is usually used $or long distance co&&unication *et!een syste&s e,g, the Internet A leased line service provides $or highlevel online activities, It is &uch cheaper to use and provides *etter "uality trans&ission, The leased lines are &uch &ore $le-i*le than dial service lines, /sers in the syste& have greater access through the &any lines provided *y the co&&on carrier, 7o!ever+ leased lines are suita*le $or use in one organisation or in one *uilding
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2ide*and these o$$er the highest trans$er rates !ith data co&&unication through coa-ial ca*les, *, Integrate$ Ser2ice# Digital Net)or. /ISDN0 it is an international e$$ort to replace the analogue technology !ith digital technology through a single set o$ standard inter$aces, c, Micro)a2e Satellite Tran#mi##ion These trans&issions are sent through the air, The trans&ission uses a line o$ light that &ust *e uno*scured, /sually these trans&issions are $ro& space satellites placed in stationary or*it and earth satellites and are co&&unicated $ro& and to satellite dishes,
Satellite
Destination
Source
Earth
This $or& o$ trans&ission can trans&it large a&ounts o$ data over !ider areas, This is in &uch use in !ide area television *roadcasting, Although trans&ission is o$ high "uality+ setting up the syste& is very e-pensive, d, Ra$io Tran#mi##ion This $or& o$ trans&ission uses radio !aves+ transportation and ta-i co&panies $or easier co&&unication use it, The police and ar&y to co&&unicate also use this, e, $, Cell!lar Tran#mi##ion The local area under the trans&ission is divided into cells, As the cellular trans&ission user &oves $ro& one cell to the other the connection is passed $ro& one cell to the other, The signals $ro& individual cells are integrated into one regular telephone syste&, g, 'hy#ical Ca-le# Trans&ission uses physical ca*les !hich are connected to the co&&unication points, There are three types o$ these ca*les1 #i. T)i#te$"'air 6ire ca-le this consists o$ a pair o$ t!isted !ires, The !ires are insulated and t!isted to avoid the *leeding o$ signals $ro& or into the each other, There are shielded !ires #!ith a special conducting !ire. and unshielded t!istedpair #/T%. that has no 32
insulation, It is the type used in ho&e telephone connections, The t!isted pair !ire ca*le is ine-pensive, 7o!ever+ it does not allo! high rates o$ data trans$er+ and is prone to inter$erence and too *ulky, #ii. Coa5ial ca-le Consists o$ an inner conductor coated !ith insulation called a dielectric #a layer o$ $oil. that is covered *y nonconductive insulation called a 0acket, This o$$ers a cleaner and crisper trans&ission than the t!isted pair !ire ca*le and has a higher data trans$er rate, 7o!ever+ it is &ore e-pensive, #iii. Fi-re otic ca-le This is &ade up o$ a glass or plastic core surrounded *y a cladding &aterial #paper+ polyethylene+ t!ine or other sheathing., They use light !hich is turned on and o$$ rapidly creating the on o$$ *it, The sheathing o$ the ca*le prevents loss o$ re$lection, Advantages >, 7igh trans&ission capacities B, S&aller ca*le si)e and lighter !eight , Very little cross talk and spying , :ittle inter$erence H, Repeaters #to *oast strength o$ the signal. are not re"uired @, Are ideal $or ha)ardous conditions since there is no sparking, These are ho!ever "uite e-pensive to purchase and set up,
COM'(TER NET6OR, SYSTEMS A net!ork is a nu&*er o$ co&puters connected through so&e channel so that they &ay share so&e o$ the resources and allo! access into the& *y users $ro& other points, A$2antage# of net)or.ing a, Resources can *e shared e,g, printers+ co&puter $iles and progra&&es, *, More even distri*ution o$ processing and other !ork *y the co&puters and users, c, More econo&ic and $uller use o$ co&puters, d, Allo! $or the provision o$ local $acilities !ithout loss o$ central control, e, Mutual support and a spirit o$ cooperation e-ist, Di#a$2antage# of net)or.ing: a, There could *e congestion at the shared resources, *, Control o$ in$or&ation and con$identiality &ay *e lost, c, The costs o$ the syste& &ay *e considera*le, d, Viruses and other $or&s o$ corruption to progra&&es spread $aster 33
6i$e Area Net)or.# /6AN0 These are net!orks that are spread over large geographical areas, The telephone syste& is one such 2AN, It is a long distant net!ork o$ interconnected co&puters on separate sites+ cities or even di$$erent countries, '!ro#e# of Imlementation of 6AN To get data $ro& its source, I&prove on the productivity o$ the syste& *y i&proving the speed o$ processing Allo! $or instant $eed*ack and e-pansion o$ the syste&, 6AN har$)are Ho#t# This provides users !ith processing so$t!are and access, The host is usually a &ain$ra&e co&puter !ith &icroco&puters connected to it, Front en$ 'roce##or# /FE'0 3 1ac. En$ 'roce##or# /1E'0 These are &inico&puters that are placed in $ront o$ #F4%. or at the *ack #34%. o$ the &ain syste& C%/, These assist the &ain syste& C%/ !ith accepting input per$or& the operations on it *e$ore $or!arding it to the &ain$ra&e C%/ $or $urther processing or a$ter the &ain syste& C%/ to assist !ith the output activities, They generally &anage co&&unications, The &ain syste& C%/ concentrates on process !ork !ithout having to handle input and output activities, Mo$em# This is short $or Modulate De&odulate, Telephone lines that are co&&on link &edia *et!een co&puters use the analogue signal !hereas co&puters use digital signals, So there is need to convert the signals, Fro& the sending co&puter+ the digital signal should *e &odulated to analogue signal $or trans&ission over the telephone link, At the receiving end the analogue signal has to *e de&odulated #converted *ack. into the digital signal, Modulation can *e done using a nu&*er o$ ðods, A&plitude &odulation #AM. !here the a&plitude is &odi$ied to represent *inary digits = and >, Fre"uency Modulation #FM. ad0usts $re"uency to represent the *its = and >, The %hase Shi$t Modulation ad0usts a $i-ed a&ount so that = and > can correspond to di$$erent phase shi$ts, Terminal# These are the &icroco&puters connected to the syste& on !hich the users can !ork to sent data or access in$or&ation, Ter&inals &ay *e du&p or intelligent, Du&p ter&inals have li&ited &e&ory and intelligence !hile intelligent ter&inals have processing and &e&ory capa*ilities that they can process data the&selves,
34
M!ltile5or it is a device that can su*divide one *ig channel so that &any people can use it at the sa&e ti&e, There are t!o types o$ &ultiple-ors1 ti&e division and $re"uency division, Ti&e Division Multiple-ors #TDM. It slices &ultiple inco&ing signals into s&all ti&e intervals that are then trans&itted over a channel and then split *y another TDM at the receiving end,
Ti&e Slots
Ti&e
Fre"uency Division Multiple-or #FDM. inco&ing signals on di$$erent $re"uency ranges are sent across a trans&ission &ediu& at the sa&e ti&e, At the receiving end another FDM splits the $re"uencies into &ultiple signals again, $ S # "
Multile!or
Multile!or
Terminal controller#+Concentrator#" are used to connect &any ter&inals to a single line+ they do not co&&unicate directly !ith the F4%, %rotocol Converters 3ecause o$ the diversity o$ technology in co&&unication+ 2ANs are using various devices+ channels+ &odes and codes, To allo! $or co&&unication *et!een and a&ong all these protocol converters are used to translate di$$erent signals $ro& one syste& to another, Typical protocol converters include 7TT% #7yper Te-t Trans$er %rotocol. used on Internet co&&unications+ TC%
35
6AN Soft)are In order $or the 2AN hard!are to operate there should appropriate so$t!are !hich should include teleco&&unications access progra&&es that handle &essages *et!een the host;s &e&ory and the re&ote devices+ this progra&&e could *e in the F4%, There is also the net!ork control progra&&e that has the !ork o$ running the net!ork o$$ the host *y checking i$ ter&inals have &essages to send+ do editing o$ inco&ing &essages, Net)or. concern# For the Manager >, Relia*ility o$ the net!ork there should *e &ini&al *reakdo!n and errors in the syste&, B, Response ti&e o$ the Net!ork there should *e less ti&e spent on picking the re"uired signals !hen re"uired, , Costs o$ the Net!ork costs o$ setting up and &aintaining the syste& &ay *e considera*le+ so the &anager should reduce these, , Co&pati*ility o$ So$t!are and hard!are hard!are and the so$t!are should *e co&pati*le #capa*le o$ !orking together. other!ise there should at least *e so&e conversion o$ either the so$t!are or the hard!are to suit the other, H, Access and Security o$ the Syste& !ith 2AN there is greater risk o$ data *eing accessed *y unauthorised people+ there should *e &easures to reduce this risk e,g, use o$ pass!ords+ physical access protection or through encryption #coding o$ data so that in the event that it is intercepted it &ay not *e understood. 6AN Toology
Pi&*a*!e
Mode%
Multile!or
Mode%
Multile!or
So!th Africa
Terminal#
Ho#t
36
LOCAL AREA NET6OR,S /LAN0 It is an interconnected group o$ &inico&puters or other ter&inals !ithin a s&all geographical area, The area could *e a roo&+ a nu&*er o$ o$$ices or a *uilding, LAN Har$)are an$ Soft)are Net)or. 6or.#tation# these are usually &icroco&puters $ro& !here a user can !ork to enter or receive data $ro& the net!ork, These could *e du&p ter&inals or diskless 2orkstations, File Ser2er# These are co&puter syste&s attached to a net!ork that control acce## to an$ other )i#e manage har$ $i#.# to allo! the !orkstations to share disk space+ progra&&es and data and to control the net)or. , 'rint Ser2er# these are co&puters that have the duty o$ &anaging the printer resources+ that is allocating print ti&e+ and carrying out other print routines, Comm!nication Ser2er# these &anage co&&unication devices in the net!ork #&ode&s+ &ultiple-ors., A &icroco&puter or even the $ile server could do this 0o* provided that it is not too *usy !ith its o!n $unctions, Ca-ling these connect the di$$erent co&puter syste&s and devices in the net!ork, So&eti&es :ANs use radio !aves and thus are !ireless, Net)or. interface Car$# these provide the necessary translation o$ signals *et!een the devices in the net!ork, They are so&eti&es called adapters, The Net)or. oerating Sy#tem These are progra&&es that &anage the operations o$ the net!ork allo!ing the user to install the net!ork+ the application so$t!are+ analyse and solve net!ork pro*le&s+ &anage the sending+ routing and delivery o$ &essages and do other routine and housekeeping duties $or the net!ork, LAN Toologie# Topologies are !ays in !hich a net!ork can *e structured or arranged depending on the resources+ the needs and the structure o$ the given organisation,
>, Star Toology there is a central node the $ile server #!hich could *e a &inico&puter or &icroco&puter. to !hich all other co&puters in the syste& are connected, All the processing and storage are done *y the host #central co&puter., There is no direct interter&inal co&&unication, The net!ork is suita*le $or use in o$$ices and ho&es, Advantages a, It is easy to trou*le shoot *, It is econo&ic and o$$ers intensive use o$ the ter&inals 37
c, Re"uires a single intelligent co&puters+ ter&inals could *e du&p there *y saving on the cost o$ the net!ork, d, 4ach ter&inal has direct and "uicker access to the host Disadvantages a, It is prone to $ailure $ailure o$ the node &ean loss and *reakdo!n to the !hole syste&, *, The ca*ling &ay *e costly c, Viruses can *e trans&itted easily !ithin the net!ork $er%inal
"ost
B, 1!# /M!lti$ro0 Toology All the co&puters are connected to a linear trans&ission &ediu& called a *us through the use o$ a tap, The tap is used to create a link up to the &ediu& and to the net!ork,
This net!ork handles higher tra$$ic, A$2antage# a, Costs o$ setting up and &aintaining the net!ork are lo!, *, 4ach ter&inal can co&&unicate directly !ith any other on the net!ork, Di#a$2antage# a, Risk o$ net!ork &al$unction *, Are &ore trou*leso&e than the star topology, c, Trou*le shooting is &ore di$$icult, d, There is the risk o$ data collision, ;: Ring Toology It is &ade up o$ a series o$ nodes connected to each other to $or& a closed loop, 4ach loop can accept data trans&itted to it $ro& an i&&ediate neigh*our and 38
$or!ard data not addressed to it to the ne-t neigh*our, Messages are trans&itted in packets or $ra&es, 4ach node has an address and packet is delivered to the node *earing the address re"uired,
A$2antage# a, There is *ypass technology so that &essages can *e passed on $ro& a $ailed !orkstation *reakdo!n o$ a !orkstation does not a$$ect the net!ork &uch, *, It is easy to install c, There is less risk o$ packet collision d, More accurate and relia*le Di#a$2antage# a, There is poor response ti&e *, There is risk o$ data interception so there should *e data encyption, c, /n!anted data &ay continue to circulate the net!ork+ thus reducing tra$$ic carrying capacity o$ the net!ork,
, Me#h Toology This topology co&*ines the ring and the star topologies, 3idirectional links are esta*lished,
This o$$ers *etter co&&unication and reduces the risk o$ data collision *ecause o$ the e-istence o$ alternative routes, The net!ork has "uick response ti&e and is very accurate, 7o!ever+ the costs o$ the ca*ling are "uite considera*le, H, Hierarchical /Tree0 Toology
39
The nodes are connected to $or& a hierarchy, Messages are passed along the *ranches until they reach their destinations, These net!orks do not need a centralised co&puter that controls co&&unications, These are also very easy to trou*leshoot and repair *ecause the *ranches can *e separated and serviced separately,
@, Mi5e$ Toologie# Various topologies are co&*ined into one net!ork,
LAN concern# for the Manager Costs o$ connection ca*les and so$t!are Co&pati*ility o$ the hard!are and so$t!are Appoint&ent o$ a net!ork &anager !here necessary, THE INTERNET The Internet is a !orld!ide net!ork o$ co&puter syste&s, Millions o$ co&puter net!orks in di$$erent parts o$ the !orld are connected *y telephone lines+ ca*les+ radio and &icro!ave links and &ode&s, 3ecause the telephone syste& is not yet $ully digitali)ed+ there is need to convert the predo&inantly digital co&puter signal to analogue and reconvert to digital, This is done *y the Mo$em #short $or Modulator de&odulator. !hich sits *et!een the co&puter and the telephone line, Mode&s &ay *e e-ternal or internal to the %C, There are &any organi)ations that o$$er internet services, These are called Internet Service %roviders #IS%s. and they usually charge a &onthly $ee $or the connection, So&e IS%s do not charge a $ee $or the service, I$ you !ant to e-plore the Internet+ a !e* *ro!ser is re"uired, A !e* *ro!ser contains progra&&es that assist in the sur$ing o$ the internet, The &ost used !e* *ro!ser is Microso$t Internet 4-plorer, 40
6e- #ite & 2e* address ( Facilities on the Internet Electronic Mail It is co&&only re$erred to as the e&ail, 4very user o$ the e&ail has a uni"ue address, 4&ail addresses have an Q+ $or e-a&ple &iriro&Qyahoo,co& One can send and receive &essages the sa&e !ay an ordinary letter is sent and received, 4&ail &essages are sent $ro& user to user on a co&puter net!ork !ith &essage *eing stored in the recipient6s &ail*o- or in*o-, The ne-t ti&e the user logs on+ he is told that there is a ne! &essage+ these &essages can *e read+ printed or replied, 4&ail allo!s $or the sending o$ attach&ents, These are $iles that contain greater detail and are *ased on a particular application package like Microso$t 2ord+ Micro$o$t 4-cel, One can even send a CV+ an assign&ent or other docu&ent using e&ail,
4&ail &akes use o$ an e-isting internet connection and so$t!are, 7o!ever+ there is a &isconception in the &inds o$ &any students that e&ail and internet are one and the sa&e thing, Internet provides &any $acilities and the e&ail is only one o$ the&, Advantages o$ e&ail >, Speed Messages are received instantly - %rovides certainty o$ delivery o$ &ail - Reading+ sending replies+ redirecting &assages is $aster, B, Cost enerally cheaper than ordinary &ail - :ess or no paper used, , Ti&e :ess ti&e spent on the phone !aiting to *e put through+ $inding people uno*taina*le+ holding the line *ecause line is engaged and leaving &essages and having to call again, , Fle-i*ility Anyone !ith a %C at ho&e can send and receive &essages out o$ o$$ice hours, - Messages can *e sent and received at any co&puter that is linked to the net!ork, Di#a$2antage# of e"mail >, Delay ( i$ a recepient takes long to log on+ the speed advantages is lost - I$ there is a pro*le& !ith the recepient6s server+ one &ay not kno! i&&ediately i$ the &essage has *een received or not, B, In$or&ation Overload ( So&eti&es there &ay *e too &any &essages - So&eti&es i&portant or urgent &essages are overlooked, , unk &ail ( There &ay lots o$ un!anted &essages received, 41
, 3reakdo!ns ( O$ten log on pro*le&s &ay result in &essages not *eing sent or received, H, Security ( There is the concern a*out security o$ con$idential in$or&ation that is sent and
Types o$ Data %rocessing <: Centrali#e$ $ata roce##ing
This is !here data is sent to and processed at a central place, Advantages o$ centralised data processing a, All re"uired in$or&ation can *e got $ro& one place *, :ittle distortion o$ in$or&ation c, 4asy to &anage and control d, Cheaper to i&ple&ent e, 4asier to en$orce standards $, Is not co&plicated
42
Di#a$2antage# a, The !hole syste& is distur*ed !hen the co&puter is do!n, *, /sers o$ the syste& have little control over the data even their o!n, c, :oss o$ data *y the processing co&puter &ay &ean loss o$ data at other points, d, Needs specialists to set up and &aintain the syste& and its environ&ent, e, %rocessing o$ data &ay *e slo! due to congestion at the central co&puter, B, Di#tri-!te$ roce##ing Data is processed at di$$erent points in the organisation, 3ranch or depart&ent &ay have a &icroco&puter or &inico&puter that processes the in$or&ation, The &inico&puter in the *ranch then sends to a host co&puter a$ter processing, "#S$ &#M'($ER 1
2
3
4
5
6
A$2antage# a, Data lost at any point &ay *e recovered $ro& the host *, Faster processing o$ data c, %rocessing &ay occur even i$ the host co&puter is do!n d, /ser have so&e control over their data e, %ro*le& can *e solved at the di$$erent points Di#a$2antage# a, The syste& needs e-pensive e"uip&ent and has high &aintenance costs, *, Manage&ent and control di$$icult c, There is dada duplication at the di$$erent points d, No uni$or&ity o$ data e, There is no overall control ti&e =: 1atch roce##ing
A central co&puter syste& nor&ally processes all transactions against a central data *ase and produces reports at intervals, In *atch processing transactions are accu&ulated over a period o$ ti&e and processed periodically, A -atch #y#tem handles the inputing+ processing+ 0o* "ueuing and trans&ission o$ the data $ro& the re&ote sites !ith little or no user intervention, 3atch processing involves, a, Data gathering $ro& source docu&ents at the re&ote site through the re&ote 0o* entry #R4. *, recording the transaction data onto so&e &ediu& e,g, &agnetic tape or disk, c, Sorting the transactions into transaction $iles d, %rocessing o$ the data 43
e, /pdating the &aster $ile, A$2antage# a, It is econo&ical !hen large a&ounts o$ data are *eing processed *, Suita*le !here reports and in$or&ation is needed periodically, c, Reduced risk o$ error due to the ti&e involved in validation and veri$ication, Di#a$2antage# a, Master $iles are o$ten out o$ date *, I&&ediate updated responses cannot *e &ade, c, /nsuita*le !here decisions and $ollo! up transactions depend on the results o$ earlier transactions e,g, in *ank !ithdra!als and deposits, d, Once the syste& $ails all output is delayed, >: On"line 'roce##ing
It is the input o$ transactions !hile the input device is connected directly to the &ain C%/ o$ the syste&, There is no necessity o$ a *atch, A$2antage# a, Ite&s can *e input &uch easier and "uicker, *, Many errors are dealt !ith *y the operator at entry c, Ti&e is saved *ecause a *atch does not have to *e produced $irst, d, /ser can recognise ano&alies in the data *eing entered Di#a$2antage# a, The syste& &ay *e &ore e-pensive than *atch processing, *, So&eti&es accuracy o$ data depends on the operator !ho &ight $ail to detect or prevent so&e errors, c, So&eti&es source docu&ent are not used e,g, in the case o$ telephone orders, ?: On"line Real time roce##ing
It is the continual receiving and rapid processing o$ data as to *e a*le to $eed*ack the result o$ that input to the source o$ that data, There is no delay *et!een the input o$ a transaction and the updating o$ the &aster $iles $or the transaction, The only delay is $or the necessary validation and veri$ication o$ the data, This allo!s $or i&&ediate processing o$ data and results generated to provide i&&ediate output to users, Data does not have to !ait+ as is the case under *atch processing, Data is $ed directly into the co&puter syste& $ro& online ter&inals !ithout the storing+ sorting #these are done online.
44
A$2antage# %rocessing is instantaneous Files and data*ases are al!ays up to date Di#a$2antage# The syste&s are e-pensive to and co&ple- to develop and put up, Data !ith errors &ay *e processed !ith da&aging e$$ect, 7ard!are costs are high+ there is need $or online ter&inals+ &ore C%/ po!er+ large online storage and *ack up $acilities, @: Time Sharing 'roce##ing
%rocessor ti&e is shared *et!een users to provide &ultiaccess #&any users accessing data at the sa&e ti&e., This can *e done *y &inico&puters and &ain$ra&e co&puter syste&s, Advantages a, 4ach user is given a chance *, More than one person can use the co&puter at the sa&e ti&e, Disadvantages The user &ay not re"uire a service at the ti&e his slice is given this results in too &uch e-cess capacity at so&e periods, THE DATA 'ROCESSING CYCLE
Data Ac"uisition #Fro& source Docu&ents.
Output Co&&unication veri$ication.
Input<
Storage
Capture#validation
checks+
%rocessing
45
Stage > Data ac"uisition this is the collection o$ data $ro& source docu&ents #receipts+ delivery notes. $or input into the co&puter syste&, Stage B Input
Ti&eliness that data is not out o$ date, Validation the "uality o$ the data is checked *e$ore it is entered or processed and errors detected and eli&inated,
*ali$ation metho$# Allo)e$ character chec.# Checks that ascertain that only e-pected characters are present in a $ield, For e-a&ple a nu&eric $ield &ay only allo! the digits =G+ the deci&al point and perhaps a &inus sign or co&&as, A te-t $ield such as a personal na&e &ight disallo! characters such as and J+ as they could *e evidence o$ a &arkup*ased security attack, An e&ail address &ight re"uire at least one Q sign and various other structural details, Regular e-pressions are e$$ective !ays o$ i&ple&enting such checks, #See also data type checks *elo!. 1atch total# Checks $or &issing records, Nu&erical $ields &ay *e added together $or all records in a *atch, The *atch total is entered and the co&puter checks that the total is correct+ e,g,+ add the ;Total Cost; $ield o$ a nu&*er o$ transactions together, Car$inality chec.
46
Checks that record has a valid nu&*er o$ related records, For e-a&ple i$ Contact record classi$ied as a Custo&er it &ust have at least one associated Order #Cardinality J =., I$ order does not e-ist $or a custo&er record then it &ust *e either changed to seed or the order &ust *e created, This type o$ rule can *e co&plicated *y additional conditions, For e-a&ple i$ contact record in %ayroll data*ase is &arked as $or&er e&ployee+ then this record &ust not have any associated salary pay&ents a$ter the date on !hich e&ployee le$t organi)ation #Cardinality =., Chec. $igit# /sed $or nu&erical data, An e-tra digit is added to a nu&*er !hich is calculated $ro& the digits, The co&puter checks this calculation !hen data are entered, For e-a&ple the last digit o$ an IS3N $or a *ook is a check digit calculated &odulus >=, Con#i#tency chec.# Checks $ields to ensure data in these $ields corresponds+ e,g,+ I$ Title Mr,+ then ender M, Control total# This is a total done on one or &ore nu&eric $ields !hich appears in every record, This is a &eaning$ul total+ e,g,+ add the total pay&ent $or a nu&*er o$ Custo&ers, Cro##"#y#tem con#i#tency chec.# Co&pares data in di$$erent syste&s to ensure it is consistent+ e,g,+ The address $or the custo&er !ith the sa&e id is the sa&e in *oth syste&s, The data &ay *e represented di$$erently in di$$erent syste&s and &ay need to *e trans$or&ed to a co&&on $or&at to *e co&pared+ e,g,+ one syste& &ay store custo&er na&e in a single Na&e $ield as ;Doe+ ohn ;+ !hile another in three di$$erent $ields1 FirstNa&e #ohn.+ :astNa&e #Doe. and MiddleNa&e #uality.5 to co&pare the t!o+ the validation engine !ould have to trans$or& data $ro& the second syste& to &atch the data $ro& the $irst+ $or e-a&ple+ using S:1 :astNa&e UU ;+ ; UU FirstNa&e UU su*str#MiddleNa&e+ >+ >. !ould convert the data $ro& the second syste& to look like the data $ro& the $irst ;Doe+ ohn ; Data tye chec.# Checks the data type o$ the input and give an error &essage i$ the input data does not &atch !ith the chosen data type+ e,g,+ In an input *o- accepting nu&eric data+ i$ the letter ;O; !as typed instead o$ the nu&*er )ero+ an error &essage !ould appear, File e5i#tence chec. Checks that a $ile !ith a speci$ied na&e e-ists, This check is essential $or progra&s that use $ile handling, Format or ict!re chec.
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Checks that the data is in a speci$ied $or&at #te&plate.+ e,g,+ dates have to *e in the $or&at DD and >B, Referential integrity In &odern relational data*ase values in t!o ta*les can *e linked through $oreign key and pri&ary key values in the pri&ary key $ield are not constrained *y data*ase internal &echanis&+ then they should *e validated, Validation o$ the $oreign key $ield checks that re$erencing ta*le &ust al!ays re$er to a valid ro! in the re$erenced ta*le, Selling an$ grammar chec. :ooks $or spelling and gra&&atical errors,
(ni!ene## chec. Checks that each value is uni"ue, This can *e applied to several $ields #i,e, Address+ First Na&e+ :ast Na&e., Ta-le Loo. ( Chec. A ta*le look up check takes the entered data ite& and co&pares it to a valid list o$ entries that are stored in a data*ase ta*le,
Stage
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%rocessing this is the key part o$ the cycle !here data is converted into in$or&ation, This is !here calculations and other logical and &anipulative operations on the data are done, Speci$ic applications are used to process the data e,g, !ord processing+ spreadsheet+ payroll packages etc
Stage Storage in$or&ation is stored on various storage &edia including hard disks+ $loppy disks+ &agnetic tapes etc, Stage H Output The processed in$or&ation is eventually displayed $or use *y the user through the various output syste&s printers+ VD/s+ sound cards L speakers, DATA 'ROCESSING 'ERSONNEL The 0o* involving the capture+ processing and output o$ data and in$or&ation involves a nu&*er o$ people, So&eti&es there &ay *e one person to do this and o$ten there &ay *e a depart&ent solely responsi*le $or data processing or $or In$or&ation technology, The data processing depart&ent interacts !ith all other depart&ents $ro& !here it gets data and $or !ho& it processes and eventually provides the in$or&ation to, The &ain $unctions o$ a D% depart&ent are1 a, Design and install a custo& *uilt syste& o$ data capture and processing, *, %rovision o$ advice to the organisation on &atters regarding the processing o$ in$or&ation e,g, the selection o$ the correct devices $or input+ process+ storage and output, c, %rovides advice on the installation o$ a package or in$or&ation syste& d, Manage the organisation;s data processing resources, A typical D%
Data %rocessing Manager
Syste&s Manager
D3A
3A SA TA
%rogra&&ing Manager
A%
S%
Operations Manager
D%S
CO
CO
CO CO
S:
D%:
CO CO
,ey4 D3A Data*ase Ad&inistrator 49
3A SA TA A% S% D%S S: D%: CO
3usiness Analyst Syste& Analyst Technical Analyst Application analyst Syste& %rogra&&er Data control Supervisor Shi$t :eader Data %rocessing :i*rarian Co&puter Operator
>, Data roce##ing Manager 7e is the head o$ the IT or D% depart&ent covering the three &ain areas o$ syste& develop&ent+ progra&&ing+ and operations &anage&ent, The Main D!tie# of the D'M a, Develop&ent and assisting in producing data processing policy $or the organisation, *, 4-ecution o$ the de$ined data processing policy c, Manage&ent o$ the data processing $unction d, :iasing !ith data user depart&ents e, 2orking !ith &anage&ent to identi$y pro*le& areas and areas o$ i&prove&ent, $, 4nsuring proper syste&s develop&ent+ syste& &aintenance and co&puter operating standards e-ist+ are kept up to date, g, 4nsuring proper security and *ackup arrange&ents are in e-istence and are tested regularly, h, 4nsuring that the syste&s are ade"uately docu&ented, i, 4nsure proper evaluation o$ the i&ple&ented syste&s, 0, %roviding suita*le training $or the data personnel, k, Coordination o$ all activities in the depart&ent l, Resolution o$ con$lict !ithin the depart&ent and *et!een the depart&ent and other depart&ents, &, %rovide guidance on issues o$ data processing n, Reco&&ends on sta$$ing issues,
B, Sy#tem Analy#t The title and $unction o$ this person &ay vary $ro& organisation to organisation or as an organisation develops $ro& stage to the other, As the co&puter is applied to the di$$erent organisational pro*le&s+ the duties o$ the analyst &ay change,
50
A *usiness analyst !ould re"uire less skill than the syste& designer or the technical analyst, These personnel deal !ith &ore or less the sa&e task *ut !ith di$$ering depth, Main D!tie# a, 4-a&ine the $easi*ility o$ potential co&puter applications and to consider all the various approaches to co&puterisation that are availa*le, *, To per$or& the proper analysis o$ user syste&s and re"uire&ents, c, Develop a cost *ene$it analysis in con0unction !ith the users, d, Design syste&+ !hich take into account not only the co&puter procedures *ut the clerical and other procedures around the co&puter syste&, e, To speci$y the check and controls to *e incorporated into the syste& in con0unction !ith the audit sta$$, $, To speci$y the &ost appropriate processing techni"ues to *e used e,g, &icro+ &ini or &ain$ra&e+ *atch or real ti&e processing, g, To ensure that there is proper co&&unication and clear instructions at each stage o$ the pro0ect e,g, progra&&e speci$ication+ $ile set up+ operating instructions+ print out volu&es, h, To ensure the syste& is properly set up and docu&ented, i, To ensure a proper environ&ent $or syste& testing and pilot running and parallel running o$ the syste& as &ay *e appropriate,
, 'rogrammer A$ter design the progra&&er co&es in, 7e uses the progra& speci$ications produced *y the analyst
Once the progra&&e is in place+ the &aintenance progra&&er !ould take the responsi*ility o$ correcting any su*se"uent pro*le&s and reco&&end any i&prove&ents, Sy#tem# 'rogrammer 7e specialises in nonapplication progra&&es e,g, operating syste&s+ data co&&unications D!tie# a, :iaising !ith co&puter supplier to keep a*reast !ith operating syste& changes, *, Support syste&s analyst and progra&&er regards "ueries on the syste& so$t!are per$or&ance and $eatures, c, Assisting the progra&&er to interpret and resolve pro*le&s !hich appear to *e caused *y the syste& so$t!are rather than application so$t!are,
H, Alication rogrammer 7e !rites progra&&es or adapts so$t!are packages to carry out speci$ic task or operations $or the co&puter users e,g, a sales analysis progra&&e $or the &arketing depart&ent, D!tie# a, discuss the progra&&e speci$ication !ith the analyst, *, To !rite the sources progra& &odule, c, To test the progra&&e and de*ug it, d, To &aintain progra&&es correcting errors+ &aking i&prove&ents L &odi$ications to allo! $or changing *usiness ðods+ circu&stances or e"uip&ent, e, 4ncode the procedure detailed *y the analyst in a language suita*le $or the speci$ied co&puter, $, :iase !ith the analyst and other users on the logical correctness o$ the progra&&e, @: Com!ter Oerator S
d, Carrying out routine &aintenance such as cleaning the tapes and read !rite heads, e, 4nsure the e"uip&ent is running e$$iciently and reporting any $aults to the technicians, $, Replace&ent o$ co&puter accessories e,g, toner catridges+ ri**ons+ ink, g, S!itching the co&puter on
?, Data-a#e A$mini#trator This is a person responsi*le $or planning+ designing and &aintaining the organisation;s data*ase, This person relates to the &anage&ent+ syste& analysts+ progra&&ers and other stakeholders in the organisation, 7e needs to have ade"uate &anagerial and technical a*ilities to suit the 0o*, 7e there$ore &ust have a sound kno!ledge o$ the structure o$ the data*ase and the D3MS, Duties a, 4nsure that the data*ase &eets the needs o$ the organisation, *, 4nsure $acilities $or the recovery o$ data c, 4nsure the $unctioning o$ report generation syste&s $or& the D3MS d, The D3A is also responsi*le $or the docu&entation o$ the D3MS through the designing and availing o$ the data dictionary and &anuals $or the users giving such direction as the general use o$ the data*ase+ access to in$or&ation+ deletion o$ records $ro& the syste& and the general validation and veri$ication o$ data, Duties o$ the personnel overlap and depending on the si)e o$ the organisation or the IT depart&ent so&e duties are done *y one person, 53
FILE AND DATA1ASE MANAGEMENT SYSTEM File Concet# The purpose o$ a co&puter $ile is to hold data re"uired $or providing in$or&ation, A co&puter $ile is a collection o$ related records, Records consist o$ $ields and the $ields are &ade up o$ characters, A character is the s&allest ele&ent o$ a $ile, A character &ay *e a letter o$ the alpha*et+ a digit or o$ a special $or& #sy&*ols., :ogical $iles sho! !hat data ite&s are contained and !hat processing &ay *e done !hile physical $iles are vie!ed in ter&s o$ ho! data is stored on storage &edia, Tye# of File#
>, Ma#ter File# ( They hold per&anent data $or use in applications such as stock control+ credit control, /sually &uch o$ the data ite&s in these $iles do not change $re"uently or !ith each transaction e,g na&e+ address or date o$ *irth, B, Tran#action file# ( These are also called &ove&ent $iles, They hold te&porary records o$ values, They are used to update the &aster $ile and are over!ritten a$ter the updating o$ the &aster $ile,
, Loo. ! file# ( they are re$erence $iles $ro& !hich such in$or&ation as prices list and &ailing list can *e o*tained, , Archi2e file# ( these are $iles that are used to store in$or&ation that has not *een in use in the recent past and !ould not *e in use in the near $uture ( so are used to store historical data, File Str!ct!re# This is the !ay a records are stored on the storage device or &ediu&, This is ho! the $iles are arranged, The arrange&ent also a$$ects the !ay these $iles !ill *e accessed,
>, SeA!ential File# ( the $iles are stored and accessed in se"uence i,e, one a$ter another, Access the $ile is dependent on the position o$ the $ile on the storage &ediu&, Accessing the $iles is *y &oving usually through spooling to the relevant $ile, This is the structure o$ $iling on &agnetic tapes, It is &ost suita*le !here all the records on the $ile are *eing considered e,g, in the preparation o$ a payroll *ut !ould *e ine$$icient !here the selection o$ one record is necessary e,g, access to one e&ployee on the payroll, 54
B, The Direct File Str!ct!re ( The $iles are rando&ly stored, Access and storage o$ the records not depend on the physical position o$ the record on the $ile, This is the $or& o$ $ile structure on &agnetic disks+ $loppy disks+ or on optical disks, 4ach record is given a speci$ic disk address *y !hich it is recogni)ed and accessed, This is the structure used to store and access records and $iles on the Auto&atic Teller Machine #ATMs. syste&s, Access to records is &uch $aster, 7o!ever+ there could *e con$lict resolution !here several records generate the sa&e address ( this pro*le& has *een dealt !ith the use o$ con$lict resolution &echanis&s on the co&puter and $iling syste&s, , In$e5e$ SeA!ential File Str!ct!re ( This co&*ines the $eatures o$ se"uential and direct $ile structures, Records are stored se"uentially on a direct access &ediu& like the hard disk and each record occupies an addressa*le location identi$ia*le *y the uni"ue disk address, An inde- is developed to keep track o$ the records and their physical locations on the storage &ediu&, The records can *e stored and accessed se"uentially starting $ro& the *eginning &oving through the records one at a ti&e or can *e stored and accessed directly e,g, the !ay the cell phone6s phone *ook is structured, N3 On all the types and structures discussed a*ove a user &ay add or re&ove a $ile or record+ &odi$y contents o$ the $ile or record+ vie! the contents o$ the data and create reports as &ay *e necessary, These operations on the data can *e done online i,e, $iles and records updated as the transactions are *eing entered $ro& a device connected onto the &ain C%/ o$ the syste&, DATA1ASE CONCE'TS
A data*ase is a single organised collection o$ structured data, It is a collection o$ related $iles that are stored in a uni$or& !ay $or ease o$ access, It can also *e de$ined as a collection o$ logically related records or $iles previously stored separately so that a co&&on pool o$ data records is $or&ed, A data*ase has a nu&*er o$ advantages over the keeping o$ separate $iles1 Data Independence data can *e de$ined and descri*ed separately $ro& the application progra&&e, 2here there is no data independence a change in any record !ould then necessitate the changing o$ the progra&&e to access the $ile, Data Redundancy The sa&e data ele&ent appears in a nu&*er o$ $iles *ut serving the sa&e purpose and usually thus staying unused, 55
Data Inconsistency this is !hen redundant data is not updated accurately so &uch that there are di$$erences in the data ele&ents on the di$$erent $iles, Advantages o$ the Data*ase a, 4asier data sharing leading to econo&ies o$ scale *, Reduced data redundancy c, I&proved data consistency d, I&proved data independence e, Inreased application progra&&er productivity $, I&proved data ad&inistration and control g, Increased e&phasis on data as a resource Disadvantages o$ Data*ases a, Concurrence pro*le&s !here &ore than one user access and atte&pt to update the sa&e record at the sa&e ti&e there is $ile edit locking to prevent this, *, O!nership pro*le&s so&eti&es so&e individuals tend to o!n the data and thus re$use access *y other individuals or depart&ents in the organisation, c, Resources pro*le& !ith data*ase e-tra resources are needed e,g, &ore !orkstations and other devices, d, Security pro*le&s there is increased e-posure to unauthori)ed entry into the data this could *e reduced *y the use o$ regularly changed pass!ords and *y physically denying access to unauthori)ed users, The Data-a#e Management Sy#tem /D1MS0
It is a co&ple- syste& o$ so$t!are that constructs+ e-pands and &aintains the data*ase, It provides a controlled inter$ace *et!een the data*ase and the user, Application Programme
DBMS
DB
Application Programme
Comonent# of a D1MS Data Dictionary this is a data*ase &anage&ent tool that has na&es and descriptions o$ all data ele&ents !ithin a data*ase,
56
Data repositories these are an e-tension o$ the data dictionary !hich provide a directory o$ co&ponent parts o$ the d3 and other in$or&ation resources in the organisation, Data languages a de$inition language is needed to place the data in the data dictionary through the use o$ co&&ands such as #ort% get% fin$ etc: Teleprocessing Monitor This is a so$t!are that controls and &anages the co&&unication *et!een re&ote ter&inals e,g, $ro& and to sales points in a large depart&ental store, Applications Develop&ent So$t!are this is a set o$ develop&ent so$t!are used to help the user progra&&er to develop data*ase so$t!are, Security So$t!are this is a set o$ so$t!are used to &ini&i)e unauthori)ed access to the data*ase, Archiving and Recovery Syste&s these syste&s are used to store *ackups o$ the original record so that i$ the original data*ase is da&aged the in$or&ation can still *e recovered, Report 2riters these allo! the user to o*tain reports $ro& the data "uicker and easier, F!nction# of the D1MS a, Allocates storage space to data *, It &aintains indices to allo! $or easy access too data ite&s, c, It allo!s $or the addition+ editing and deletion o$ $iles in the data*ase, d, %rovides an inter$ace !ith user progra&&es !hich &ay *e !ritten in di$$erent progra&&ing languages, e, %rovides $or the processing o$ $iles in di$$erent !ays1 #i. processing o$ a co&plete $ile #se"uentially or serially. #ii. process re"uired records #selective+ se"uential or rando&. #iii. retrieve individual records
$, %rovides security $or the data in the data*ase through1 #i. denying unauthori)ed access to data #ii. preventing data corruption #iii. providing data recovery in the case o$ $ailure
57
g, 'eeps a record o$ statistics o$ the use o$ data in the data*ase+ this assists in the re&oval o$ redundant #duplicated. data+ it also keeps $re"uently used data &ore accessi*le, The Data-a#e A$mini#trator This is a person responsi*le $or planning+ designing and &aintaining the organisation;s data*ase, This person relates to the &anage&ent+ syste& analysts+ progra&&ers and other stakeholders in the organisation, 7e needs to have ade"uate &anagerial and technical a*ilities to suit the 0o*, 7e there$ore &ust have a sound kno!ledge o$ the structure o$ the data*ase and the D3MS, Re#on#i-ilitie# of the D1A e, 4nsure that the data*ase &eets the needs o$ the organisation, $, 4nsure $acilities $or the recovery o$ data g, 4nsure the $unctioning o$ report generation syste&s $or& the D3MS h, The D3A is also responsi*le $or the docu&entation o$ the D3MS through the designing and availing o$ the data dictionary and &anuals $or the users giving such direction as the general use o$ the data*ase+ access to in$or&ation+ deletion o$ records $ro& the syste& and the general validation and veri$ication o$ data, Data-a#e #tr!ct!re# /Entity relation#hi Mo$el#0
Records in the data*ase &ay *e set in di$$erent !ays depending on the relationships *et!een the records the&selves, >, One to One relation#hi this is !here one record is related to one other record e,g, single parent record to one child record Record Recor ddd
This can *e represented in a relational entity &odel+ in 4R diagra&s Record
>
Represents
> Record
This could *e !here one sales representative deals !ith one custo&er $or e-a&ple,
58
B, One to many relation#hi# one parent to &any children Record
Record
Record
Record
In the form of an E"R $iagram
Represents
>
Record
NRecords
e,g, one sales representative $or relating to &any custo&ers, , Many to one !here there are &any parents to one child Record
Record
Record
Record
In 4R diagra& Records
Represents
M
Record M
e,g, &any sales representatives relating !ith on custo&er+ &any lecturers relating to one student, , Many to &any !ith t!o or &ore parents relating to t!o or &ore children Record
Record
Record
Record
Record
Record
59
In 4R diagra&1 Records
M
Represents
Records M
This could *e the &any sales reps relate to &any custo&ers, Di#tri-!te$ *er#!# Centrali8e$ Data-a#e A distri*uted data*ase is !hen the data*ases are scattered !hereas a centrali)ed d3 is !here the data*ases are located in one area and usually under &anage&ent o$ a group o$ people, A d3 &ay *e distri*uted in t!o !ays1 Replicated or partitioned,
A replicated d3 is one that has *een copied and is kept at di$$erent geographical locations, This allo!s $or easier recovery i$ one $ails and reduces data trans&ission costs+ as there !ould *e little long distance trans&ission thus is also $aster, This+ ho!ever+ it is e-pensive in ter&s o$ co&puter resources, A partitioned d3 is one that is split into seg&ents and each seg&ent distri*uted to the relevant location, This reduces trans&ission costs and provides a $aster turnaround ti&e in input+ processing and output, There is reduced data inconsistency and redundancy, 7o!ever+ there is need $or &ore co&puter resources that are costly, An Online d3 this is a d3 that is allo!s $or the i&&ediate updating o$ $iles $ro& re&ote ter&inals since input !ill *e directly into the syste& e,g, stock &arket in$or&ation, DATA SEC(RITY
This re$ers to &easures to reduce unauthori)ed access to+ use and destruction o$ an organisation6s data and data resources, Data is a valua*le resource like any other asset o$ an organi)ation, Data like &oney can *e stolen and e-changed $or so&e value, Organisations have so&e pieces o$ data that are con$idential and these need to *e secure, 4very organi)ation needs to take security o$ hard!are+ so$t!are and data seriously *ecause the conse"uences o$ *reaches o$ security can *e e-tre&ely da&aging to a *usiness, This &ay lead to loss o$ production+ cash $lo! pro*le&s+ loss o$ custo&ers and reputation,
60
Threats to security co&e $ro& outside #e-ternal. and inside #internal. the organisation Securing data entails &aking sure that the co&puters are in the right environ&ent+ there are right so$t!are &easures to reduce loss or the$t o$ data, Sec!rity of E!iment
There is need to look a$ter the co&puter hard!are !ell to avoid loss o$ data or the co&puters the&selves, Re"uire&ents $or a Co&puter 4nviron&ent #Co&puter Roo&. >, Ventilation ( a good roo& has to *e ade"uately ventilated, I$ ventilation is poor the co&puter &ay over heat and thus $ail to operate properly, B, %o!er supply ( po!er supply should o$ the right voltage and supplied $ro& sa$e socket outlet, %o!er ca*les should not cross the roo& to avaid inter$ering !ith $ree &ove&ents, , /se o$ /ninterupted %o!er Supplies #/%S. ( in the event o$ unanticipated po!er loss or po!er surge there should *e so&e stand*y po!er alternative so that the users6s in$or&ation is not lost, , Carpet ( Carpets are good dust a*sor*ers+ this thus reduces dust in the roo&+ dust inter$eres !ith the operation o$ electronic e"uip&ent, H, Curtains ( Curtains reduce the a&ount o$ light getting to the screens and other co&puter e"uip&ent, :ight da&ages screens, @, :ocka*le doors ( doors should *e locka*le to avoid unauthori)ed access to the co&puters or the$t or vandalis& o$ the co&puter syste&s, The key should *e kept !ith so&e responsi*le person, , Metal 3ars and Shutters ( Fit roo& !ith &etal *ars and shutter, ?, An alar& syste& ( an alar& syste& &ay *e installed to !arn o$ an intrision, G, ID *adges ( all users to use ID *adges $or access to the roo& or *uilding, >=, Security guards ( have a t!enty$our hour guard to the roo&, >>, Attach co&puters per&anently to desks using cla&ps to avoid the$t o$ the co&puter#s., >B, 7ave all e"uip&ent serial nu&*ers $or use i$ e"uip&ent is stolen, >, 7ave $ire $ighting syste&s in place to deal !ith ant risks o$ $ire to the e"uip&ent, >, Reduce levels o$ &oisture ( &oisture da&ages electronic e"uip&ent, Sec!rity of Data
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Data itsel$ is at risk o$ accidental or deli*erate loss and the$t, Acci$ental Lo##
Accidental loss &ay *e caused *y1 - docu&ent is accidentally deleted - co&puter *reaks do!n or po!er $ails - $ile or disk *eco&es corrupted - $ile is destroyed *y $ire or $lood, To reduce the risk o$ loss to accidental loss there is the use o$ *ack up o$ data ( there should *e a saved copy o$ the original $ile that is kept on a di$$erent &ediu& and place, Deli-erate Damage
This is loss o$ data *y viruses or hackers *ir!#e# A co&puter virus is a har&$ul progra& that copies itsel$ onto other progra&&es and destroys the& or inter$eres !ith their proper $unctioning,
%resence o$ viruses can *e noticed *y1 #a. Displaying o$ &essages #*. Deleting data and progra&&e $iles #c. Failure o$ co&puter to detect peripherals #d. Display o$ irritating &essages or i&ages #e. 4-aggerated $ile and docu&ent si)es, #$. /n!anted $or&atting o$ hard disk #g. %laying &usic #h. Co&puter $ails to *oot up Viruses are trans&itted $ro& co&puter to co&puter, They copy the&selves "uickly, 4$$ects o$ viruses &ay *e &ild to severe, So&e viruses are har&less and co&puters &ay operate nor&ally, Characteri#tic# of 2ir!#e#
#a. Copies itsel$ #*. 7ides
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To reduce the risk o$ viral in$ection1 #a. /se antivirus so$t!are #*. /se genuine so$t!are #c. 2rite protect all so$t!are progra&s #d. Make regular COM'(TERS AND HEALTH AND SAFETY
Co&puter and co&puter e"uip&ent have negative health e$$ects on the users, Research is still *eing carried out to deter&ine the e-tent o$ the e$$ects on the health o$ users, The &ain e$$ects are1 #a. Repetitive Strain In0ury #RSI. #*. 4ye strain $ro& VD/ use #c. 3ad posture #d. Risk o$ an accident #e. 4-posure to radiation
#a. Reetiti2e Strain In9!ry This re$ers to disorders that a$$ect the hands+ !rists+ ar&s+ shoulders or neck o$ co&puter operators, It is in$la&&ation o$ the 0oints and is caused *y &aking the sa&e s&all &ove&ents over and over again, This can cause pain+ nu&*ness+ s!elling and the ina*ility to li$t or grip o*0ects, In so&e cases+ operators have *eco&e per&anently disa*led, To re$!ce RSI - &ake sure the desk and chair are at suita*le heights - sit at a co&$orta*le distance $ro the key*oard - &ake sure that lo!er ar&s are hori)ontal and !rists straight !hen using a key*oard or &ouse, - /se a !rist rest i$ necessary so that you do not rest you !rists on the edge o$ the ta*le or key*oard, - Take $re"uent *reaks to stretch your ar&s and $ingers
#*. Eye Strain From *D( /sing the VD/ $or long periods at a ti&e &ay a$$ect a user6s eyes and in so&e instances cause headaches,
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To reduce eye strain1 - desks and VD/s area arranged to avoid glare or *right re$lections on the screen, - Arrange desks so that user is not looking at !indo!s or lights - /se curtains and !indo! *linds - Sharply $ocus VD/ so that characters do not &ove and $licker - 7ave regular eye tests - Ad0ust screen *rightness and contrast to suit lighting conditions - Ad0ust the angle o$ the screen to your sitting height - 'eep the screen clean - /se a docu&ent holder so that you do not lean over to read docu&ents, - Take a *reak every B= to = &inutes, #c. 'o#t!re Sitting incorrectly or !ithout right support at a co&puter ter&inal $or long periods &ay result in *ack+ neck and upper ar& pains, To reduce posture related pro*le&s1 - /se ad0usta*le chairs to ad0ust height - /se ad0usta*le *ackrests - /se s!ivel chairs - /se $ootrest - Al!ays sit !ell - Change sitting positions regularly - Take $re"uent short *reaks #d. Ri#. of Acci$ent I$ it &ay *e necessary to shi$t a co&puter+ i$ not done properly &ay result in in0ury to the !orker, There &ay also *e pro*le&s relating to po!er and $alling over o$ co&puter e"uip&ent that is not put up properly, #e. Ri#. of E5o#!re Ra$iation So&e co&puter e"uip&ent produces radiation that has longter& e$$ects on users or on un*orn *a*ies, SYSTEMS DE*ELO'MENT LIFE CYCLE
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The syste&s develop&ent li$e cycle is a pro0ect &anage&ent techni"ue that divides co&ple- pro0ects into s&aller+ &ore easily &anaged seg&ents or phases, Seg&enting pro0ects allo!s &anagers to veri$y the success$ul co&pletion o$ pro0ect phases *e$ore allocating resources to su*se"uent phases, So$t!are develop&ent pro0ects typically include initiation+ planning+ design+ develop&ent+ testing+ i&ple&entation+ and &aintenance phases, 7o!ever+ the phases &ay *e divided di$$erently depending on the organi)ation involved, For e-a&ple+ initial pro0ect activities &ight *e designated as re"uest+ re"uire&entsde$inition+ and planning phases+ or initiation+ conceptdevelop&ent+ and planning phases, 4nd users o$ the syste& under develop&ent should *e involved in revie!ing the output o$ each phase to ensure the syste& is *eing *uilt to deliver the needed $unctionality, Note1 4-a&iners should $ocus their assess&ents o$ develop&ent+ ac"uisition+ and &aintenance activities on the e$$ectiveness o$ an organi)ation6s pro0ect &anage&ent techni"ues, Revie!s should *e centered on ensuring the depth+ "uality+ and sophistication o$ a pro0ect &anage&ent techni"ue are co&&ensurate !ith the characteristics and risks o$ the pro0ect under revie!, INITIATION 'HASE
Care$ul oversight is re"uired to ensure pro0ects support strategic *usiness o*0ectives and resources are e$$ectively i&ple&ented into an organi)ation;s enterprise architecture, The initiation phase *egins !hen an opportunity to add+ i&prove+ or correct a syste& is identi$ied and $or&ally re"uested through the presentation o$ a *usiness case, The *usiness case should+ at a &ini&u&+ descri*e a proposal6s purpose+ identi$y e-pected *ene$its+ and e-plain ho! the proposed syste& supports one o$ the organi)ation6s *usiness strategies, The *usiness case should also identi$y alternative solutions and detail as &any in$or&ational+ $unctional+ and net!ork re"uire&ents as possi*le, The presentation o$ a *usiness case provides a point $or &anagers to re0ect a proposal *e$ore they allocate resources to a $or&al $easi*ility study, 2hen evaluating so$t!are develop&ent re"uests #and during su*se"uent $easi*ility and design analysis.+ &anage&ent should consider input $ro& all a$$ected parties, Manage&ent should also closely evaluate the necessity o$ each re"uested $unctional re"uire&ent, A single so$t!are $eature approved during the initiation phase can re"uire several design docu&ents and hundreds o$ lines o$ code, It can also increase testing+ docu&entation+ and support re"uire&ents, There$ore+ the initial re0ection o$ unnecessary $eatures can signi$icantly reduce the resources re"uired to co&plete a pro0ect, I$ provisional approval to initiate a pro0ect is o*tained+ the re"uest 65
docu&entation serves as a starting point to conduct a &ore thorough $easi*ility study, Co&pleting a $easi*ility study re"uires &anage&ent to veri$y the accuracy o$ the preli&inary assu&ptions and identi$y resource re"uire&ents in greater detail, The $easi*ility support docu&entation should *e co&piled and su*&itted $or senior &anage&ent or *oard study, The $easi*ility study docu&ent should provide an overvie! o$ the proposed pro0ect and identi$y e-pected costs and *ene$its in ter&s o$ econo&ic+ technical+ and operational $easi*ility, The docu&ent should also descri*e alternative solutions and include a reco&&endation $or approval or re0ection, The docu&ent should *e revie!ed and signed o$$ on *y all a$$ected parties, I$ approved+ &anage&ent should use the $easi*ility study and support docu&entation to *egin the planning phase, 'LANNING 'HASE: The planning phase is the &ost critical step in co&pleting develop&ent+ ac"uisition+ and &aintenance pro0ects, Care$ul planning+ particularly in the early stages o$ a pro0ect+ is necessary to coordinate activities and &anage pro0ect risks e$$ectively, The depth and $or&ality o$ pro0ect plans should *e co&&ensurate !ith the characteristics and risks o$ a given pro0ect, %ro0ect plans re$ine the in$or&ation gathered during the initiation phase *y $urther identi$ying the speci$ic activities and resources re"uired to co&plete a pro0ect, A critical part o$ a pro0ect &anager6s 0o* is to coordinate discussions *et!een user+ audit+ security+ design+ develop&ent+ and net!ork personnel to identi$y and docu&ent as &any $unctional+ security+ and net!ork re"uire&ents as possi*le, DESIGN 'HASE The design phase involves converting the in$or&ational+ $unctional+ and net!ork re"uire&ents identi$ied during the initiation and planning phases into uni$ied design speci$ications that developers use to script progra&s during the develop&ent phase, %rogra& designs are constructed in various !ays, /sing a topdo!n approach+ designers $irst identi$y and link &a0or progra& co&ponents and inter$aces+ then e-pand design layouts as they identi$y and link s&aller su*syste&s and connections, /sing a *otto&up approach+ designers $irst identi$y and link &inor progra& co&ponents and inter$aces+ then e-pand design layouts as they identi$y and link larger syste&s and connections, Conte&porary design techni"ues o$ten use prototyping tools that *uild &ockup designs o$ ite&s such as application screens+ data*ase layouts+ and syste& architectures, 4nd users+ designers+ developers+ data*ase &anagers+ and net!ork ad&inistrators should revie! and re$ine the prototyped designs in an iterative process until they agree on an accepta*le design, Audit+ security+ and "uality assurance personnel should *e involved in the revie! and approval process, 66
Manage&ent should *e particularly diligent !hen using prototyping tools to develop auto&ated controls, %rototyping can enhance an organi)ation6s a*ility to design+ test+ and esta*lish controls, 7o!ever+ e&ployees &ay *e inclined to resist adding additional controls+ even though they are needed+ a$ter the initial designs are esta*lished, Designers should care$ully docu&ent co&pleted designs, Detailed docu&entation enhances a progra&&er6s a*ility to develop progra&s and &odi$y the& a$ter they are placed in production, The docu&entation also helps &anage&ent ensure $inal progra&s are consistent !ith original goals and speci$ications, Organi)ations should create initial testing+ conversion+ i&ple&entation+ and training plans during the design phase, Additionally+ they should dra$t user+ operator+ and &aintenance &anuals, Alication Control Stan$ar$# Application controls include policies and procedures associated !ith user activities and the auto&ated controls designed into applications, Controls should *e in place to address *oth *atch and online environ&ents, Standards should address procedures to ensure &anage&ent appropriately approves and control overrides, Re$er to the IT 7and*ook6s Operations 3ooklet $or details relating to operational controls, Designing appropriate security+ audit+ and auto&ated controls into applications is a challenging task, O$ten+ *ecause o$ the co&ple-ity o$ data $lo!s+ progra& logic+ client
Standards should *e in place to ensure end users+ net!ork ad&inistrators+ auditors+ and security personnel are appropriately involved during initial pro0ect phases, Their involve&ent enhances a pro0ect &anager;s a*ility to de$ine and incorporate security+ audit+ and control re"uire&ents, The sa&e groups should *e involved throughout a pro0ect6s li$e cycle to assist in re$ining and testing the $eatures as pro0ects progress, Application control standards enhance the security+ integrity+ and relia*ility o$ auto&ated syste&s *y ensuring input+ processed+ and output in$or&ation is authori)ed+ accurate+ co&plete+ and secure, Controls are usually categori)ed as preventative+ detective+ or corrective, %reventative controls are designed to prevent unauthori)ed or invalid data entries, Detective controls help identi$y unauthori)ed or invalid entries, Corrective controls assist in recovering $ro& un!anted occurrences, Input Controls 67
Auto&ated input controls help ensure e&ployees accurately input in$or&ation+ syste&s properly record input+ and syste&s either re0ect+ or accept and record+ input errors $or later revie! and correction, 'roce##ing Control#
Auto&ated processing controls help ensure syste&s accurately process and record in$or&ation and either re0ect+ or process and record+ errors $or later revie! and correction, %rocessing includes &erging $iles+ &odi$ying data+ updating &aster $iles+ and per$or&ing $ile &aintenance, O!t!t Control#
Auto&ated output controls help ensure syste&s securely &aintain and properly distri*ute processed in$or&ation, DE*ELO'MENT 'HASE: The develop&ent phase involves converting design speci$ications into e-ecuta*le progra&s, 4$$ective develop&ent standards include re"uire&ents that progra&&ers and other pro0ect participants discuss design speci$ications *e$ore progra&&ing *egins, The procedures help ensure progra&&ers clearly understand progra& designs and $unctional re"uire&ents,
%rogra&&ers use various techni"ues to develop co&puter progra&s, The large transactionoriented progra&s associated !ith $inancial institutions have traditionally *een developed using procedural progra&&ing techni"ues, %rocedural progra&&ing involves the line*yline scripting o$ logical instructions that are co&*ined to $or& a progra&, %ri&ary procedural progra&&ing activities include the creation and testing o$ source code and the re$ine&ent and $inali)ation o$ test plans, Typically+ individual progra&&ers !rite and revie! #desk test. progra& &odules or co&ponents+ !hich are s&all routines that per$or& a particular task !ithin an application, Co&pleted co&ponents are integrated !ith other co&ponents and revie!ed+ o$ten *y a group o$ progra&&ers+ to ensure the co&ponents properly interact, The process continues as co&ponent groups are progressively integrated and as inter$aces *et!een co&ponent groups and other syste&s are tested, Advance&ents in progra&&ing techni"ues include the concept o$ o*0ectoriented progra&&ing, O*0ectoriented progra&&ing centers on the develop&ent o$ reusa*le progra& routines #&odules. and the classi$ication o$ data types #nu&*ers+ letters+ dollars+ etc,. and data structures #records+ $iles+ ta*les+ etc,., :inking prescripted &odule o*0ects to prede$ined dataclass o*0ects reduces develop&ent ti&es and &akes progra&s easier to &odi$y, Re$er to the So$t!are Develop&ent Techni"ues 68
section
$or
additional
in$or&ation
on
o*0ectoriented
progra&&ing,
Organi)ations should co&plete testing plans during the develop&ent phase, Additionally+ they should update conversion+ i&ple&entation+ and training plans and user+ operator+ and &aintenance &anuals, De2eloment Stan$ar$#: Develop&ent standards should *e in place to address the responsi*ilities o$ application and syste& progra&&ers, Application progra&&ers are responsi*le $or developing and &aintaining enduser applications, Syste& progra&&ers are responsi*le $or developing and &aintaining internal and opensource operating syste& progra&s that link application progra&s to syste& so$t!are and su*se"uently to hard!are, Managers should thoroughly understand develop&ent and production environ&ents to ensure they appropriately assign progra&&er responsi*ilities,
Develop&ent standards should prohi*it a progra&&er;s access to data+ progra&s+ utilities+ and syste&s outside their individual responsi*ilities, :i*rary controls can *e used to &anage access to+ and the &ove&ent o$ progra&s *et!een+ develop&ent+ testing+ and production environ&ents, Manage&ent should also esta*lish standards re"uiring progra&&ers to docu&ent co&pleted progra&s and test results thoroughly, Appropriate docu&entation enhances a progra&&er;s a*ility to correct progra&&ing errors and &odi$y production progra&s, Coding standards+ !hich address issues such as the selection o$ progra&&ing languages and tools+ the layout or $or&at o$ scripted code+ and the na&ing conventions o$ code routines and progra& li*raries+ are outside the scope o$ this docu&ent, 7o!ever+ standardi)ed+ yet $le-i*le+ coding standards enhance an organi)ation6s a*ility to decrease coding de$ects and increase the security+ relia*ility+ and &aintaina*ility o$ application progra&s, 4-a&iners should evaluate an organi)ation6s coding standards and related code revie! procedures, Li-rary Control#
:i*raries are collections o$ stored docu&entation+ progra&s+ and data, %rogra& li*raries include reusa*le progra& routines or &odules stored in source or o*0ect code $or&ats, %rogra& li*raries allo! progra&&ers to access $re"uently used routines and add the& to progra&s !ithout having to re!rite the code, Dyna&ic link li*raries include e-ecuta*le code progra&s can auto&atically run as part o$ larger applications, Li-rary control# #ho!l$ incl!$e4
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*er#ion Control#
:i*rary controls $acilitate so$t!are version controls, Version controls provide a &eans to syste&atically retain chronological copies o$ revised progra&s and progra& docu&entation, Develop&ent version control syste&s+ so&eti&es re$erred to as concurrent version syste&s+ assist organi)ations in tracking di$$erent versions o$ source code during develop&ent, The syste&s do not si&ply identi$y and store &ultiple versions o$ source code $iles, They &aintain one $ile and identi$y and store only changed code, 2hen a user re"uests a particular version+ the syste& recreates that version, Concurrent version syste&s $acilitate the "uick identi$ication o$ progra&&ing errors, For e-a&ple+ i$ progra&&ers install a revised progra& on a test server and discover progra&&ing errors+ they only have to revie! the changed code to identi$y the error, Soft)are Doc!mentation
Organi)ations should &aintain detailed docu&entation $or each application and application syste& in production, Thorough docu&entation enhances an organi)ation6s a*ility to understand $unctional+ security+ and control $eatures and i&proves its a*ility to use and &aintain the so$t!are, The docu&entation should contain detailed application descriptions+ progra&&ing docu&entation+ and operating instructions, Standards should *e in place that identi$y the type and $or&at o$ re"uired docu&entation such as syste& narratives+ $lo!charts+ and any special syste& coding+ internal controls+ or $ile layouts not identi$ied !ithin individual application docu&entation, Manage&ent should &aintain docu&entation $or internally developed progra&s and e-ternally ac"uired products, In the case o$ ac"uired so$t!are+ &anage&ent should ensure #either through an internal revie! or thirdparty certi$ication. prior to purchase+ that an ac"uired product6s docu&entation &eets their organi)ation;s &ini&u& docu&entation standards, For additional in$or&ation regarding ac"uired so$t!are distinctions #open
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The testing phase re"uires organi)ations to co&plete various tests to ensure the accuracy o$ progra&&ed code+ the inclusion o$ e-pected $unctionality+ and the interopera*ility o$ applications and other net!ork co&ponents, Thorough testing is critical to ensuring syste&s &eet organi)ational and enduser re"uire&ents, I$ organi)ations use e$$ective pro0ect &anage&ent techni"ues+ they !ill co&plete test plans !hile developing applications+ prior to entering the testing phase, 2eak pro0ect &anage&ent techni"ues or de&ands to co&plete pro0ects "uickly &ay pressure organi)ations to develop test plans at the start o$ the testing phase, Test plans created during initial pro0ect phases enhance an organi)ation6s a*ility to create detailed tests, The use o$ detailed test plans signi$icantly increases the likelihood that testers !ill identi$y !eaknesses *e$ore products are i&ple&ented, Testing groups are co&prised o$ technicians and end users !ho are responsi*le $or asse&*ling and loading representative test data into a testing environ&ent, The groups typically per$or& tests in stages+ either $ro& a topdo!n or *otto&up approach, A *otto&up approach tests s&aller co&ponents $irst and progressively adds and tests additional co&ponents and syste&s, A topdo!n approach $irst tests &a0or co&ponents and connections and progressively tests s&aller co&ponents and connections, The progression and de$initions o$ co&pleted tests vary *et!een organi)ations, 3otto&up tests o$ten *egin !ith $unctional #re"uire&ents *ased. testing, Functional tests should ensure that e-pected $unctional+ security+ and internal control $eatures are present and operating properly, Testers then co&plete integration and endto end testing to ensure application and syste& co&ponents interact properly, /sers then conduct acceptance tests to ensure syste&s &eet de$ined acceptance criteria, Testers o$ten identi$y progra& de$ects or !eaknesses during the testing process, %rocedures should *e in place to ensure progra&&ers correct de$ects "uickly and docu&ent all corrections or &odi$ications, Correcting pro*le&s "uickly increases testing e$$iciencies *y decreasing testers6 do!nti&e, It also ensures a progra&&er does not !aste ti&e trying to de*ug a portion o$ a progra& !ithout de$ects that is not !orking *ecause another progra&&er has not de*ugged a de$ective linked routine, Docu&enting corrections and &odi$ications is necessary to &aintain the integrity o$ the overall progra& docu&entation, Organi)ations should revie! and co&plete user+ operator+ and &aintenance &anuals during the testing phase, Additionally+ they should $inali)e conversion+ i&ple&entation+ and training plans, IM'LEMENTATION 'HASE
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The i&ple&entation phase involves installing approved applications into production environ&ents, %ri&ary tasks include announcing the i&ple&entation schedule+ training end users+ and installing the product, Additionally+ organi)ations should input and veri$y data+ con$igure and test syste& and security para&eters+ and conduct post i&ple&entation revie!s, Manage&ent should circulate i&ple&entation schedules to all a$$ected parties and should noti$y users o$ any i&ple&entation responsi*ilities, A$ter organi)ations install a product+ pree-isting data is &anually input or electronically trans$erred to a ne! syste&, Veri$ying the accuracy o$ the input data and security con$igurations is a critical part o$ the i&ple&entation process, Organi)ations o$ten run a ne! syste& in parallel !ith an old syste& until they veri$y the accuracy and relia*ility o$ the ne! syste&, 4&ployees should docu&ent any progra&&ing+ procedural+ or con$iguration changes &ade during the veri$ication process, 'RO7ECT E*AL(ATION 'HASE Manage&ent should conduct posti&ple&entation revie!s at the end o$ a pro0ect to validate the co&pletion o$ pro0ect o*0ectives and assess pro0ect &anage&ent activities, Manage&ent should intervie! all personnel actively involved in the operational use o$ a product and docu&ent and address any identi$ied pro*le&s, Manage&ent should analy)e the e$$ectiveness o$ pro0ect &anage&ent activities *y co&paring+ a&ong other things+ planned and actual costs+ *ene$its+ and develop&ent ti&es, They should docu&ent the results and present the& to senior &anage&ent, Senior &anage&ent should *e in$or&ed o$ any operational or pro0ect &anage&ent de$iciencies, MAINTENANCE 'HASE The &aintenance phase involves &aking changes to hard!are+ so$t!are+ and docu&entation to support its operational e$$ectiveness, It includes &aking changes to i&prove a syste&6s per$or&ance+ correct pro*le&s+ enhance security+ or address user re"uire&ents, To ensure &odi$ications do not disrupt operations or degrade a syste&6s per$or&ance or security+ organi)ations should esta*lish appropriate change &anage&ent standards and procedures,
Change &anage&ent #so&eti&es re$erred to as con$iguration &anage&ent. involves esta*lishing *aseline versions o$ products+ services+ and procedures and ensuring all changes are approved+ docu&ented+ and disse&inated, Change controls should address all aspects o$ an organi)ation6s technology environ&ent including so$t!are progra&s+ hard!are and so$t!are con$igurations+ operational standards and procedures+ and pro0ect &anage&ent activities, Manage&ent should esta*lish change controls that address &a0or+ routine+ and e&ergency so$t!are &odi$ications and so$t!are patches, 72
Ma0or &odi$ications involve signi$icant changes to a syste&6s $unctionality, Manage&ent should i&ple&ent &a0or &odi$ications using a !ellstructured process+ such as an SD:C ðodology, Routine changes are not as co&ple- as &a0or &odi$ications and can usually *e i&ple&ented in the nor&al course o$ *usiness, Routine change controls should include procedures $or re"uesting+ evaluating+ approving+ testing+ installing+ and docu&enting so$t!are &odi$ications, 4&ergency changes &ay address an issue that !ould nor&ally *e considered routine+ ho!ever+ *ecause o$ security concerns or processing pro*le&s+ the changes &ust *e &ade "uickly, 4&ergency change controls should include the sa&e procedures as routine change controls, Manage&ent should esta*lish a**reviated re"uest+ evaluation+ and approval procedures to ensure they can i&ple&ent changes "uickly, Detailed evaluations and docu&entation o$ e&ergency changes should *e co&pleted as soon as possi*le a$ter changes are i&ple&ented, Manage&ent should test routine and+ !henever possi*le+ e&ergency changes prior to i&ple&entation and "uickly noti$y a$$ected parties o$ all changes, I$ &anage&ent is una*le to thoroughly test e&ergency &odi$ications *e$ore installation+ it is critical that they appropriately *ackup $iles and progra&s and have esta*lished *ackout procedures in place, So$t!are patches are si&ilar in co&ple-ity to routine &odi$ications, This docu&ent uses the ter& patch to descri*e progra& &odi$ications involving e-ternally developed so$t!are packages, 7o!ever+ organi)ations !ith inhouse progra&&ing &ay also re$er to routine so$t!are &odi$ications as patches, %atch &anage&ent progra&s should address procedures $or evaluating+ approving+ testing+ installing+ and docu&enting so$t!are &odi$ications, 7o!ever+ a critical part o$ the patch &anage&ent process involves &aintaining an a!areness o$ e-ternal vulnera*ilities and availa*le patches, Maintaining accurate+ uptodate hard!are and so$t!are inventories is a critical part o$ all change &anage&ent processes, Manage&ent should care$ully docu&ent all &odi$ications to ensure accurate syste& inventories, #I$ &aterial so$t!are patches are identi$ied *ut not i&ple&ented+ &anage&ent should docu&ent the reason !hy the patch !as not installed,. Manage&ent should coordinate all technology related changes through an oversight co&&ittee and assign an appropriate party responsi*ility $or ad&inistering so$t!are patch &anage&ent progra&s, uality assurance+ security+ audit+ regulatory co&pliance+ net!ork+ and enduser personnel should *e appropriately included in change &anage&ent processes, Risk and security revie! should *e done !henever a syste& &odi$ication is i&ple&ented to ensure controls re&ain in place, 73
DIS'OSAL 'HASE The disposal phase involves the orderly re&oval o$ surplus or o*solete hard!are+ so$t!are+ or data, %ri&ary tasks include the trans$er+ archiving+ or destruction o$ data records, Manage&ent should trans$er data $ro& production syste&s in a planned and controlled &anner that includes appropriate *ackup and testing procedures, Organi)ations should &aintain archived data in accordance !ith applica*le record retention re"uire&ents, It should also archive syste& docu&entation in case it *eco&es necessary to reinstall a syste& into production, Manage&ent should destroy data *y over!riting old in$or&ation or degaussing #de&agneti)ing. disks and tapes, Re$er to the IT 7and*ook6s 8In$or&ation Security 3ooklet9 $or &ore in$or&ation on disposal o$ &edia, RECENT DE*ELO'MENTS IN INFORMATION TECHNOLOGY
>, The Internet De$inition Facilities ∗ 3ulletin 3oards ( Maga)ines+ ne!spapers W 2e* Television ∗ Music W So$t!are do!nloading #share!are. ∗ Discussion roups W Shopping Malls W Research ∗ :i*raries ∗ Tuition and Virtual :earning #elearning. W o* Opportunities W 4&ail ∗ 4co&&erce W Date line ∗ 2eather reports B, Telecomm!ting This involves !orking $ro& ho&e !hile connected to the o$$ice through co&puter net!orks, This &eans the !orkers do not need to travel to !orkplaces, This has the advantage o$ saving ti&e to the !orker in ter&s o$ travel especially in highly congested cities, It also saves costs o$ $uel to the !orker, 7o!ever+ traditional supervision ðods do not apply, , Teleconferencing This is also kno!n as con$ravision, It is a $acility through !hich people in distant places can hold a con$erence like discussion !hile seeing each other on co&puter screens, The *iggest advantage o$ this $or& o$ technology is in the saving o$ con$erence costs like venue hire+ travel and su*sistence, There is also the *ene$it o$ *ody language that the people using this technology have,
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