INFORMATION TECHNOLOGY Information technology is the use of computer technology and digital equipment to handle and process information. For example, information technology is used when ‘hours worked’ by an employee is entered into accounting software and, together with his wage rate, his monthly wage is calculated and a payslip produced. EXAMPLES OF DIFFERENT TYPES OF INFORMATION Strategic (used to plan the objectives of the business) – profitability of each part of the business; size, growth and competitive structure of the market in which the business operates; investments made by the business and returns; feasibility reports; market research Tactical (used to decide how the resources of the business should be employed) – staff turnover; short-term profit and cash flow forecasts; pricing information Operational (used to carry out day-to-day activities) – stock levels; results of quality control checks USE OF INPUT DEVICES Keyboard – Used to input data into spreadsheet and database applications (e.g. employee records, exam scores, etc.); Used to prepare a document (e.g. a letter, book) on word processing applications Touch screen – Used to input transactional data e.g. buying transport tickets; retrieving cash from an Automated Teller Machines (ATM) Magnetic Ink Character Recognition – Used to read magnetic ink characters on the bottom of each cheque in a cheque book Optical Mark Reader – Reads paper-based forms marked with a pencil; Used to process multiple choice exam papers, questionnaires or National Lottery forms Optical Character Recognition – Recognises written characters by software that processes information obtained by a scanner; Used to transform notes into a word document Bar Code Readers – Used by supermarkets/retailers with Electronic Point of Sale Technology to compute the total amount owed and produce a bill as well as automatically adjust stock records; Used as security measures for access to certain areas Electronic Funds Transfer at Point of Sale – Used to print out details of a plastic card transaction; checks card against a list of lost and stolen cards and ensures that the amount to be paid is within the credit limit
Magnetic stripe cards – Used for identification (e.g. use in bank and cash cards) and for controlling access (e.g. swipe cards for doors and ticket barriers) Smart cards – Used as credit cards, ID cards and security keys and for information storage Voice recognition – Used with speech simulation by companies to answer phones and provide information; Used by the handicapped; Used in cases where people need to use their hands Web data capture – Electronic forms on the Internet or an Intranet can be used to collect responses to questions and the responses imported in electronic format to the required database ______________________________________________________________________________ Modem – a device or program that enables a computer to transmit data over, for example, telephone or cable lines. Computer information is stored digitally, whereas information transmitted over telephone lines is transmitted in the form of analog waves. A modem converts between these two forms. Antenna (or aerial) – is an electrical device which converts electric power into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver. In transmission, a radio transmitter supplies an electric current oscillating at radio frequency (i.e. high frequency AC) to the antenna's terminals, and the antenna radiates the energy from the current as electromagnetic waves (radio waves). In reception, an antenna intercepts some of the power of an electromagnetic wave in order to produce a tiny voltage at its terminals, that is, the power is applied to a receiver to be amplified. Transceiver – a device that can both transmit and receive data Web browser – a software application for retrieving, presenting and traversing information resources (identified by a Uniform Resource Identifier (URI/URL) and may be a web page, image, video or other piece of content) on the World Wide Web e.g. Google Chrome Search engine – software system that is designed to search for information on the World Wide Web e.g. Google A web browser is usually a software program that runs on your computer while a search engine is a software program that runs on a server somewhere else. A browser normally provides access to a specific search while a search engine stores information and indexes for searchers to find. Storage media (e.g. hard disks) are hardware used to keep data, instructions and information from a computer while storage devices record and/or retrieve items to and from storage media (hard disk drives). In a network, the server has more power, more storage space and expanded communications capabilities.
Feature
Usenet
Internet Relay Chat
Interactivity
Asynchronous, delayed
Synchronous, immediate
1 to several hundred lines
1-2 lines
External organization
Hierarchy of newsgroups by subject
Flat list of channels
Internal organization
Subject-oriented “threads”
Temporally sequenced
Maintenance
By popular vote
User activity
Authorities
Usually unmoderated (no authority)
Operators
Broadcasts
Frequent cross-posting
No multi-channel messages
Length
6
When you post a message to a newsgroup, the message goes to your local news server, and this server sends copies of the message to all servers it knows about. The message slowly propagates through the net, until all the news servers in the world have a copy. In contrast, some websites have "message boards", which may look like newsgroups. They serve the same basic purpose, but do not work as well. Message boards have become more popular than newsgroups, simply because they are easier to find. To use a message board, you just click on a link from the main site. Message boards belong to a particular website. To use a newsgroup, you must start up a newsreader, which is a separate program from the web browser. Here are the major differences between newsgroups and message boards: Flexibility - You can connect to a newsgroup with any newsreader program. If you do not like the features of one program, it is fairly easy to switch to another. On a message board, the features are determined by the site hosting the board. You have no choice. Speed - When you connect to a newsgroup, your newsreader downloads all of the new messages automatically. This allows you to quickly flip through several hundred messages, reading only the items that interest you and skipping others. On a message board, every time you display a new message, your web browser must connect to the board, and download the message individually. This usually means a 2-10 second pause between each message you read. It may not sound like much, but if you subscribe to a busy group, reading 100 messages could take over an hour! Robustness - If a news server breaks, the rest of the world can continue to use the newsgroup through other news servers. Since web message boards are stored on a single server, any time this server has a problem, the entire board is shut down. People use social networking sites, podcasts/vodcasts and blogs/vlogs to publish their thoughts and different forms of media on the Web.
Tablet PCs (and a digital pen) are useful for taking notes in lectures, meetings and conferences where typing is not practical. It also reduces the risk of RSI and facilitates the input of a drawing. Handheld computers serve the needs of mobile employees, such as meter readers and parcel delivery people. Applications of computers in society:
Education o Taking online classes o Research online o Producing notes (for teachers) and taking notes (for students in class) Finance o Software to balance cheque books, pay bills, track personal income and expenses, manage investments, and evaluate financial plans o Online banking to access account balances, pay bills and copy monthly transactions o Online investing to buy and sell stocks and bonds without a broker Government o Allows citizens to file taxes, apply for permits and licenses, pay parking tickets, buy stamps, report crimes, apply for financial aid and renew vehicle registration and driver’s licenses online o Emergency police call centres use computers to dispatch calls for fire, police and medical assistance o Countries have online databases of criminal records Heath Care o To maintain and access patient records o To monitor patients’ vital signs in hospital rooms and homes o To research and diagnose health conditions o To implement computerized devices, such as pacemakers, that allow patients to live longer o To conduct surgeries with greater precision o Telemedicine and telesurgery Science o Implants that mimic functions of body parts o Use of camera pills (which take pictures inside your body) Publishing o Graphics designing o Creating and editing film o Making works available for a wider audience via the Web Travel o Use of onboard navigation systems
o Use of the Web to reserve a car, hotel and/or flight o Use of the Web to find directions and maps Manufacturing o CAM used in fabrication and assembly to reduce costs, shorten production time and remain competitive o Used in oil drilling, power generation, food production and automobile manufacturing
Users can connect to the internet using:
Dial-up access using a standard telephone line Broadband connections o DSL – Digital Subscriber Line (telephone lines) o Cable model (cable television network) o Fibre to the Premises or FTTP (fibre-optic cables) o Fixed wireless (dish-shaped antenna to communicate via radio signals) o Wireless modem (cellular network) o Radio signals (radio signals) o Satellite modem (satellite dish)
IP address -
First group of numbers – the network Last group of numbers – the specific computer
Domain name -
First set of letters – the type of internet server e.g. www Last section of the domain name – top-level domain which identifies the type of organization e.g. .com
The Domain Name System (DNS) is the method that the internet uses to store domain names and their corresponding IP addresses. IP addresses and domain names identify computers connected to the internet while URLs are addresses for specific web sites and web pages. Two types of search tools are search engines and subject directories. Search engines locate the web pages while web browsers allow for their access and viewing. Recent edits of a wiki are collected so that they can be reviewed by someone for accuracy. A media sharing web site is a type of online social network which allows sharing of media such as photos, music and videos.
Streaming is the process of transferring data in a continuous and even flow. A podcast is recorded audio, usually an MP3 file, stored on a Web site that can be downloaded to a computer or portable media player. A plug-in or add-on is a program that extends the capability of a browser. Simple Mail Transfer Protocol is a communications protocol used by some outgoing mail servers. Post Office Protocol is a communications protocol used by some incoming mail servers. To start a chat (in a chat room), you connect to a chat server through a program called a chat client (usually included in the browser). To use VoIP or Internet telephony, users need a high-speed Internet connection, Internet telephone service, a microphone or telephone, Internet telephone software and a sound card or a telephone adapter. After purchasing or downloading software, it is installed. Registering is optional and usually entitles you to product support. Product activation is a technique used by manufacturers to ensure that the software is not installed on more computers than legally licensed. Computers with the necessary built-in wireless capability or network or other adaptor can connect to wireless Internet access points or a WLAN. These may be hot spots (using WiFi, WiMAX or Bluetooth) or mobile wireless networks (high speed). Collaborative software includes tools that enable users to share documents via online meetings and communicate with other connected users. Collaboration via email and document management systems also allow for collaboration. Groupware is software that helps groups of people work together on projects and share information over a network. It enables communication, management of projects and scheduling of meetings. Voice mail converts voice messages from analog form to digital form and stores it in a voice mailbox. Computers are networked to: facilitate communications, share hardware, software, data and information, and transfer funds. XML allows Web programmers to create one version of a Web page that can be displayed in a form appropriate for a variety of display devices. XML has a focus on content with a primary purpose of transportation and storage. Developers may customize tags. HTML, however, has a focus on appearance with a purpose of displaying data. Tags are pre-defined.
Electronic data interchange is a standard which defines how data transmits across telephone lines or other means. A Value Added Network is a privately owned wide area network owned by a third-party business that provides specific networking services not readily available on public networks such as secure data and information transfer, storage, e-mail, and management reports. The VAN is set up by a firm in charge of managing the network. Subscriptions are sold to other firms wishing to use the network. The managers of the VAN perform error checking, editing, routing and protocol conversion. Each computer or device on a LAN is called a ‘node’. Client/Server Networks – A server or host computer controls access to the hardware, software and other resources on the network and provides a centralized storage area for programs, data and information. The computers that rely on the server for resources are called ‘clients’. These are used for large networks. *The Network OS may only be installed on the server. Peer-to-Peer Networks – Each computer or peer ha equal responsibilities and capabilities, sharing hardware, data and information with other computers on the network. It is a simple, inexpensive network that typically contains fewer than 10 computers. The Network OS is installed on all computers. (pg 348 of Computing Book) Internet peer-to-peer Networks or File Sharing Networks – Users access each other’s hard disks and exchange files (shared files) directly over the Internet. They copy files from someone else’s hard disk to their hard disks. Network topologies include:
BUS or LINE – There is a single central cable (or bus) to which all computers and other devices connect. o Bus transmits data, instructions and information in both directions o Data is broadcast to all nodes but only the one with the correct address acts upon it; data transmitted includes the address of the receiving device o Popular on LANs o Inexpensive as it requires the least amount of cable o Easy to install o Computers and other devices can be attached and detached at any point without disturbing the rest of the network o Failure of one device usually does not affect the rest of the bus network
o If the bus breaks or becomes inoperable, the entire network remains inoperative and cable failure is difficult to isolate. o Network performance degrades under heavy load RING – A cable forms a closed loop with all computers and devices arranged along the ring. o Data travels from device to device in one direction until it reaches its destination o There is no dependence on a central computer or server; each node controls transmission to and from itself o Very high transmission rates are possible o If a computer or device fails, the whole network may fail o If one node breaks down, transmission between devices is disrupted o Can span a larger distance than a bus network o Fast transmission o Difficult to install o Used for LANs but also for WANs STAR – All of the computers and devices (notes) on the network connect to a central device (a hub or a switch), thus forming a star. A hub (may be used to extend the network) repeats all data, information and instructions that it receives and sends them to all ports to which it is connected. A switch only sends data, information and instructions to the address specified. This results in less congestion. o Consistent performance even when network is being heavily used o Little or no problems with ‘collisions’ or intercepting of data since messages are sent directly to the central computer o Easy to install and maintain as nodes can be added and removed with little or no disruption o If a node fails, only the node is affected making it simple to isolate faults o If the hub/switch fails, the entire network is inoperable o Costly to install because of the length of cable required o Common for WANs in large companies e.g. a mainframe computer at the Head Office linked to computers at each branch which may be linked in a LAN
Intranets:
Internal networks of organizations to which Internet and Web technologies are applied; internet facilities are provided using Internet Protocol Make company available accessible to employees Facilitate working in groups Features may include: o Electronic publishing of organizational materials such as telephone directories, event calendars, procedure manuals, etc. o A connection to the internet o Groupware applications e.g. project management, chat rooms, newsgroups
It is similar to the Internet in that: o It has a web server o It supports multimedia web pages coded in HTML o It is accessible via a web browser o Users update information by creating and posting a web page o Saves wasting time browsing aimlessly through thousands of files o Enables unsuitable material to be screened out
Extranets:
Customers, suppliers or authorised third-parties are allowed to access part of the intranet E.g. package shipping companies allow customers to print air bills, schedule pickups and track shipped packages
NETWORK STANDARDS AND PROTOCOLS A network standard defines guidelines that specify the way computer access the medium to which they are attached, the type(s) of medium used, the speeds used on different types of networks and the type(s) of physical cable and/or the wireless technology used. A protocol is a standard that outlines characteristics of how two network devices communicate. It allows equipment from different suppliers to be networked. It may define:
Data format Coding schemes Error handling Sequencing techniques Physical connections Cabling Mode of transmission
Some network standards are:
Ethernet o no central computer or device on the network should control when data can be transmitted o each node attempts to transmit data when it determines the network is available to receive communications o based on a bus topology but may also be used in the star network o most popular network standard for LANs o inexpensive and easy to install and maintain Token Ring o Computers and devices on the network share or pass a special signal, called a token, in a unidirectional manner and in a preset order
o The device with the token can transmit data over the network o Based on the ring but can be used in a start topology o Token ring networks can connect up to 72 devices and some up to 260 connections Transmission Control Protocol/ Internet Protocol (TCP/IP) o Defines how data is routed from one end of a network to the other, ensuring the data arrives correctly o Describes rules for diving messages into packets; providing addresses for each packet, checking for an detecting errors, sequencing packets, and regulating the flow of messages along the network (all known as packet switching) o Packets contain the data, recipient (destination), origin (sender), and the sequence information used for reassembly o Packets travel via routers 802.11 (used by Wi-Fi networks) o A series of network standards that specifies how two wireless devices communicate over the air with each other o Computers or devices with appropriate wireless capabilities communicate via radio waves with over computers or devices o A Wi-Fi mesh network allows mesh nodes route data to the next available node until the data reaches its destination Bluetooth – a protocol o Defines how two Bluetooth devices use short-range radio waves to transmit data o Each device contains a small chip that allows communication with other Bluetooth devices Ultra-wideband (UWB) o Specifies how two UWB devices use short-range radio waves to communicate at high speeds with each other IrDA o Used to transfer data wirelessly between computers and other devices via infrared light waves o Requires line-of-sight transmission Radio Frequency Identification (RFID) - protocol o Defines how a network uses radio signals to communicate with a tag or transponder placed n or attached to an object, an animal or a person o The tag consists of an antenna and a memory chip containing the information to be transmitted via radio waves Worldwide Interoperability for Microwave Access (WiMAX) o Specifies how wireless devices communicate over the air in a wide area o Computer and devices with WiMax wireless capability communicate via radio waves and a WiMAX tower
Functions of communications software include:
Helping users to establish a connection to another computer or network Managing the transmission of data, instructions and information Providing an interface for users to communicate with each other
Communications software includes:
E-mail FTP Web browser Newsgroup and message board Chat rooms Instant messaging Video conferencing VOIP/ Internet telephony
Types of lines that use the telephone network for data communications:
Dial-up lines – A temporary connection uses one or more analog telephone lines for communications; a modem at the sending eng dials the telephone number of the modem at the receiving end to establish the connection Dedicated lines – A type of always-on connection that is established between two communications devices. These usually have higher bandwidths than dial-up lines and are more reliable as no switches are being operated. In addition, the line is more secure as it is not shared with other organizations. o ISDN (Integrated Services Digital Network) lines – ISDN is a set of standards for digital transmission of data over standard copper telephone lines using multiplexing (carrying of multiple signals at once); capable of sending voice, video and computer data. These are used with digital modems, network termination devices and terminal adapters. o DSL (Digital Subscriber Line) – transmits at fast speeds, providing voice and data communications; uses a line that is not shared by other users in the neighbourhood o FTTP (Fiber to the Premises) – extremely high speed Internet access to a user’s physical permanent location o T-carrier lines – long-distance digital telephone lines that carry multiple signals over a single communications line and have very fast data transfer rates; homes and small businesses may use fractional T1 lines o ATM (Asynchronous Transfer Mode) – a service that carries voice, data, video and multimedia at very high speeds
COMMUNICATIONS DEVICES
Modems (Modems, other than dial-up modems, usually include built-in Wi-Fi technology) o Dial-up Modems (also used in fax machines to convert a scanned digitized image into an analog signal to be sent to a recipient’s fax machine) o Digital Modems (including ISDN and DSL modems) o Cable Modems (sends and receives digital data over the cable television network) o Wireless Modems (uses the cell phone network to connect to the Internet wirelessly from a mobile device) Network (Interface) Cards or Network Adaptors– enable a computer or device that does not have built-in networking capability to access a network; coordinates the transmission and receipt of data, instructions and information to and from the computer or device containing the network card; may be for wireless or wired networks; usually follows a particular network communications standard; must match the type of network and medium Wireless Access Points – Central communications devices that allow computers and devices to transfer data wirelessly among themselves or to transfer data wirelessly to a wired network Routers – Communications devices that forward packets between networks using IP addresses; transmit data to its correct destination on the network; allow multiple computers to share a single high-speed Internet connection such as through a cable or DSL modem; many are protected by built-in firewalls and anti-virus protection; can route packets of the same protocol over networks with dissimilar architectures (e.g. Ethernet to token ring) Gateways or protocol converters – Communications devices used to connect networks using different protocols by repackaging data so that it may be read correctly at the receiving end
Types of home networks include:
Ethernet network – each computer must have network capabilities of a NIC which connects to a hub Powerline cable network – uses the same lines that bring electricity into the house Phoneline network – uses existing telephone lines in the home
The wireless access point must be connected to the router. Advantages of networking include:
Convenience as all computers and devices may be connected to the internet at the same time and share a single high-speed Internet connection Money is saved as only one set of peripherals need to be bought and can be shared Multiplayer games may be played with players on other computers
VoIP may be used It is easier to back up data held on a file server than on many individual machines It is easier and may be cheaper to store application programs on one computer and make them available to all users rather than having copies installed on each computer
Disadvantages of networking include: Users become dependent on them; if the file server develops a fault, users will be unable to access many files and run application programs If the network stops operating, it may not be possible to access various hardware and software resources A badly managed network may operate less efficiently that stand-alone machines and an increase in network traffic may degrade performance Security may be compromised Factors influencing latency of transmission:
Distance between the two points Type of transmission media Number of nodes through which the data must travel over the media Type of transmission i.e. synchronous or asynchronous Speed of the modem Nature of the transmission line
Baseband media transmit one signal at a time while broadband media transmits multiple signals simultaneously. Types of transmission media:
Wired o Twisted pair cable – network cabling and telephone systems o Coaxial cable – cable television networking since it can be cabled over longer distances than that of the twisted pair o Fibre optic cable – used to replace telephone lines; to provide internet access to home and business users; as the transmission media in high traffic networks Can carry significantly more signals Fast data transmission Less susceptible to noise/interference Small size Wireless o Infrared – line-of-sight date transmission o Broadcast radio – distributes radio signals through the air over long distances o Cellular radio – used for mobile communications
o Microwaves – radio waves that provide high-speed signal transmission; signals are sent from one microwave station to another; use line-of-sight transmission; users include universities, cable TV providers and telephone companies; mobile telephones use microwave radio links o Communications satellite – a space station that receives microwave signals, amplifies them and broadcasts them over a wide area; applications include air navigation, weather forecasting, GPSs and internet communications. Open Systems Interconnection (OSI) Reference Model for Networks 1. Top layer – application layer – interface between the user and network 2. Presentation layer – translates data into a language the receiving computer can process, and may also perform compression or encryption 3. Session layer – establishes and maintains communications sessions 4. Transport layer – ensures that data arrives correctly and in proper sequence 5. Network layer – routes the message from sender to receiver 6. Data link layer – supervises the transmission of the message to the next network node by specifying network technology and grouping data accordingly 7. Physical layer – encodes the packets into a signal that will be recognized by the medium that will carry them TCP/IP Stack 1. Application layer – HTTP, Telnet, FTP, Email 2. Transport layer – TCP, UDP; divides data into packets 3. Network layer – IP, Arp; provides source and destination addressing and sequencing and routing of packets 4. Data link layer – NIC Applications of electronic data communication include: e-mail, supermarket electronic point of sale (EPOS) terminals, cash dispensers, facsimile, and video conferencing. Data communication also takes place between the CPU and its peripheral devices. Types of data communication:
Serial – bits are sent via an interface one bit at a time over a single wire from the source to the destination
Parallel – several bits are sent simultaneously over a number of parallel wires; used inside the computer and for very short distances (a few metres); skew may result
The bit rate is the speed at which data is transmitted serially, measured in bits per second. The baud rate is the rate at which the signal changes (baud rate x number of bits per signal).
In asynchronous data transmission, one character at a time is sent, with each character being preceded by a start bit and followed by one or two stop bits. In synchronous data transmission, timing signals synchronise the transmission at the sending and receiving end of communication. This is used in LANs. A parity bit is used as a check against incorrect transmission. Handshaking is the exchange of signals between devices to establish their readiness to send or receive data. It is one method of ensuring that both the sender and receiver are ready before transmission begins. Modes of Network Operation Baseband – one-channel system where the whole bandwidth is dedicated to one data channel and one signal is carried at a time; fast but can only operate over short distances Broadband – multi-channel system where several channels are combined onto one carrier signal; the bandwidth is shared by several data channels The topology of a network is defined as the structure –both the physical layout and how communication is done –of the inter-connections of components of a network. ‘Carrier sense multiple access with collision detection’ (CSMA-CD) is a collision system used by Ethernet networks. To ease the problem of slow network speeds due to a large number of computers and heavy traffic, the network can be segmented by inserting a bridge or router between each segment. Electronic data interchange is the transmission of business data from one computer system to another computer system via a WAN. A Virtual Private Network allows a connection (VPN tunnel) to another network using the Internet providing a secure connection to the company network server, as if they had a private line. A firewall is hardware and/or software that protect a network’s resources from intrusion by users on another network such as the Internet. A proxy server, a typical component of the firewall, screens all incoming and outgoing communications into and out of the network. The Hypertext Transfer Protocol - provides a standard for Web browsers and servers to communicate. The definition of HTTP is a technical specification of a network protocol that software must implement. It enables files to be transferred from a web server to a browser in order to view the web page. In HTTP, information is transferred – not downloaded.
HTTP is an application layer network protocol built on top of TCP. HTTP clients (such as Web browsers) and servers communicate via HTTP request and response messages. It basically provides an interface between the user and the internet. FTP works in both directions – from server to computer and vice versa. HTTP only works from server to computer. Noise is also known as ‘attenuation’ or ‘interference’ in terms of characteristics of transmission media. SYSTEMS DEVELOPMENT LIFE CYCLE A project request is sometimes submitted when a new project is desired or needed. Reasons for developing a (new) system:
Information requirements may have changed and can no longer be met by the old system Hardware may have become obsolete Security may have been breached A fault may have occurred in recent output or processing Corporate management of some governing body may have mandated a change Need to be competitive in the market
Persons involved in developing a system: Representatives from each department in which the proposed system will be used i.e. the users Systems analyst o designs and develops the information system o convert user requests into technical specifications o acts as the liaison between users and IT professionals Programmer A project leader – who is chosen from the project team to manage and control the budget and schedule of the project A deliverable is a tangible form of output from any stage in the Systems Development life cycle and may be in the form of a chart, diagram, report or program file. Stages 1. Identifying the problem/ Statement of problem 2. Feasibility study a. FUNCTIONS – It measures how suitable the development of a system will be tot the company. It checks for operational feasibility, schedule feasibility, technical
feasibility and economic feasibility. It is done to determine the exact nature of the problem or improvement and decide whether it is worth pursuing. It checks to ensure that the project is worthwhile, that is, whether it can be done and will meet goals in a timely manner without incurring great costs. b. DELIVERABLES – A feasibility report is produced including the features of the existing system and the feasibility of a new or modified system. 3. Planning a. FUNCTIONS i. Its goal is to deliver an acceptable system to the user in an agreed-upon time frame, while maintain costs. ii. It also allocates resources such as money, people and equipment. b. DELIVERABLES i. Project Plan – This is produced at this stage to record goals, objectives and expectations of the project called the ‘scope’; required activities; the order of activities; and time and cost estimates for each activity. It is useful in planning and scheduling a project effectively and assists in the coordination, monitoring and control of activities according to the plan. c. TOOLS i. GHANT Chart – This is a bar chart that uses horizontal bars to show project phases or activities and the time required for each. It shows the time relationships of a project’s activities. It is useful in the control, monitoring and coordination of activities according to plan. 4. Analysis a. FUNCTIONS i. Study current system ii. Determine user requirements iii. Recommend solution b. DELIVERABLES i. System proposal – After the system analyst has thoroughly studied the current system and determined all user requirements, he/she uses a system proposal to communicate possible solutions for the project. The solutions are further analysed and the most feasible solution is recommended. c. TOOLS – The data collection tools (the first four) are used to understand the requirements of the system and to ensure that they are met.
i. Questionnaires – This allows for collection of a standard set of information from many employees. ii. Interviews – This allows for acquisition of information and facilitates clarification of responses and feedback. iii. Observation – This helps in the understanding of how tasks are generally performed. iv. Review/investigation of printed material – The review of company documents such as organization charts, memos and meeting minutes, enables systems analysts to learn about the history of the project and the company’s strengths, weaknesses and operations. Regular sources of information are also consulted for the latest on hardware and software. v. Process modelling – This form of analysis describes processes that transform inputs into outputs. 1. Entity relationship diagrams – These show the logical structure of a database, that is, the connections among entities or data objects in a system. It is important for the systems analyst to understand the relationships between objects that handle data and how they use the data. 2. Data flow diagrams – These show the movement of data between sources and stores. They help the systems analyst to understand how data is handled and in which parts of the system. Systems analysts use these to review processes with users. 3. Decision tables and trees – These are used to show the conditions or rules of processes. They list a variety of conditions and the actions that correspond to each condition in a table form or graphically. vi. Object modelling – These describe objects which contain both data (attributes or properties) and the procedures (operations or methods) that read or manipulate that data. 5. Design a. FUNCTIONS i. Acquire hardware and software – Technical specifications must be identified; vendor proposals must be solicited, tested and evaluated; and a decision made. ii. Develop details of system – The physical design including designs for the databases, input and output interfaces and programs are specified.
b. DELIVERABLES – These include diagrams and charts showing the structure and components of the new system. Some are reports, diagrams, mock-ups, layout charts and dictionary entries. c. TOOLS i. CASE tools – Computer-aided software engineering tools are designed to support one or more activities of the SDLC. Features may include project dictionaries composed on all deliverables, graphics, prototyping, quality assurance, code generators (creates computer programs from design specifications) and housekeeping (provides backup and recovery functions). ii. Prototyping – A prototype is a working model of a proposed system. Users can work with the prototype to ensure that it meets their needs and systems designers can see any errors and correct them before the final design as it is cheaper and easier to make corrections at this stage. It is actually quicker and easier to implement a solution more quickly when a prototype was already created. However, difficulties may arise as prototypes have no documentation. 6. Development a. FUNCTION – Perform programming b. TOOLS – flowcharts, pseudocode, programming languages 7. Implementation (including testing) a. FUNCTIONS i. Install and test new system – Individual programs should be tested as well as how they work together. Unit tests, systems tests, integration tests and acceptance tests are performed. Both valid and invalid data are tested. ii. Train users – This involves showing users exactly how to use the new hardware and software in the system. iii. Convert to new system – This can be in the form of direct, parallel, phased or pilot conversion. b. DELIVERABLES i. Documentation – This is the collection and summarization of data and information and should be well written, thorough, consistent and understandable by everyone. A project notebook contains all documentation of a project. Documentation is referred to when worked with and modifying current systems. It includes end-user documentation, and operation and installation manuals.
ii. Information system (software) test plans – This is the compilation of all test data (both valid and invalid) and the responses that should be made. 8. Review and maintenance a. Perform maintenance activities – fixing errors in and improving on a system’s operations; users need to be consulted to decide if the system is performing according to users’ expectations; corrective maintenance, adaptive maintenance and perfective maintenance are carried out b. Monitor system performance – systems must be secure from unauthorized persons both inside and outside the organisation c. Assess system security The project dictionary contains all documentation and deliverables of a project. All components of DFDs and ERDs have entries in the project dictionary. INFORMATION SYSTEMS 1. Monitoring and control systems – Enable the coordination of industrial parts and processes 2. Data processing systems a. Input – data from day-to-day business activities i.e. transactional data b. Aims – process faster, reduce clerical costs and improve customer service c. Uses – to record a transaction, confirm an action or cause a response and maintain data d. Examples – to calculate paychecks and print invoices 3. Management information systems – An information system that generates, accurate, timely and organized information so the users can make decisions, solve problems, supervise activities and track progress a. Capabilities – quickly computing and comparing data to produce meaningful information often in the form of reports b. Use – to create information that managers and other users need to perform their jobs c. Output – detailed report (which lists transactions and notes about them); summarised report (consolidates data to facilitate quick and easy reviewing); exception report (identifies data outside of a normal condition enabling managers
to focus on situations that require immediate decisions or actions); ad hoc report (contains information requested in a quick response time) 4. Decision support systems – information systems which analyse and summarise internal and external sources of data for the purpose of making decisions a. Features – statistical analyses, spreadsheets, graphics, models 5. Executive information systems – supports strategic information needs of executive management a. Input – usually external sources like the Internet b. Output – charts and tables that show trends, ratios and statistics 6. Expert systems – an information system that captures and stores the knowledge of human experts and then imitates human reasoning and decision making; consists of a knowledge base and inference rules a. Uses – answering customer questions, training employees and diagnosing illnesses 7. Data warehouses – contain huge databases that store and manage data required to analyse historical and current transactions and to make decisions 8. Embedded systems – microprocessors found in everyday devices System software – programs that control or maintain the operations of the computer and its devices and serve as the interface between the user, application software and the computer’s hardware. An operating system is a set of programs containing instructions that work together to coordinate all the activities among computer hardware resources. Functions of an OS include:
Starting a computer
Providing a user interface
Managing programs
Managing memory
Coordinating tasks
Configuring devices
Administering security
Utilities (systems software that allows a user to perform maintenance type tasks) include:
File manager
Personal firewall
Disk scanner e.g. Disk Cleanup
Disk defragmenter
Backup utility
Antivirus programs
A command line interface is used to configure devices, manage system resources, and troubleshoot network connections. A technician setting up a server may use command line interface. Firewall – a piece of hardware and/or software that protects a network’s resources from intrusion by users on another network. They often include proxy servers which are servers outside the company’s network that controls which communications pass into the company’s network. A personal firewall is a utility that detects and protects a personal computer and its data from unauthorised intrusions. Identification verifies that the individual is a valid user while authentication verifies that the individual is the person he or she claims to be. Biometric devices may not work if persons have illnesses. For example, a cut on your finger might cause a fingerprint reader to reject you; hand geometry readers may transmit germs; a sore throat may cause a voice recognition system to reject you. Encryption is a process of converting readable data into unreadable characters to prevent unauthorised access via transposition, substitution, expansion, compaction and other ways of handling data. The recipient of encrypted data needs an encryption key – a programmed formula used to decrypt ciphertext. Wireless security measures:
A wireless access point should be configured so that it does not broadcast a network name.
The security standard WPA (Wi-Fi Protected Access) should be used.
Access control refers to security measures taken to define and limit who can access and use a computer, when they can access it and what actions they can take while accessing it. It is the prevention of unauthorised use of a resource, including the prevention of use of a resource in an unauthorised manner Physical access control methods are those which limit access to a place or area where computers or other restricted objects may be stored or destruction by natural and environmental hazards. Logical access control methods refer to electronic access controls whose purpose is to limit access to data files and computer programs to individuals with the genuine authority to access such information. Access control methods include:
Physical o Swipe or key cards o Biometric readers
Logical o Passwords o Encryption
Data integrity refers to the property that data has not been altered or destroyed in an unauthorised manner. It is the assurance that information can only be accessed or modified by those authorized to do so. Data integrity may be maintained by access control methods, backing up, and using uninterruptible power supplies to prevent power surges from affecting data. Data security is the result of effective protection measures that safeguard data/information from undesired occurrences and exposure to accidental or intentional disclosure to unauthorised persons, accidental or malicious alteration, unauthorised copying, loss by theft and/or destruction by hardware failures, software deficiencies, operating mistakes, or physical damage by fire, water, smoke, excessive temperature, electrical failure, or sabotage. Accountability is the property that ensures that the actions of an entity can be traced and that individuals can be held responsible for their actions such as unauthorised access of data.
Data corruption is the deterioration of computer data as a result of some external agent. Hazards to data integrity include not only computer-based problems such as viruses and hardware or software incompatibility, flaws, or failures, but also environmental threats such as power outages, dust, water, and extreme temperatures. To protect data from corruption, you should ensure that only authorized people have access to your data and that the physical environment is safe from environmental hazards. Data validation makes sure that the data is clean, correct and meaningful, while data verification ensures that all copies of the data are as good as the original. Problem solving is a mental process involving a systematic approach to identifying the problem, analyzing it to gain an understanding of its scope and subsequently finding solutions to it. A data flow diagram is a graphical representation of how data moves through a system. It is used to:
Determine the logical requirements of a system to be built
Communicate with users and managers
Analyse existing and proposed systems
A context level diagram is the top level DFD showing only a single major process that defines boundaries between the system and the entities with which it interacts. A first level DFD shows the major processes in a system and is derived by the levelling of the context level diagram. DFDs are levelled, exploded, decomposed functionally or partitioned to get to lower levels which contain more information and may give more details on individual processes.
The components of a DFD include:
External entities (sources or sinks/destinations) – These are the units from which data is received or to which data is sent.
Process – This refers to an operation performed on the data and is expressed as a verb.
Data store – This is the file where data is held.
Data flow – This represents movement between entities, processes and stores and is labelled to describe what data is involved.
Data flow diagramming errors include a:
Black hole – process with only input data flow
Miracle – a process with only output data flow from it
Data stores or external entities connected directly to each other
Data flow or objects labelled incorrectly e.g. a data flow with a verb or a process with a noun
Grey hole – inputs insufficient to produce outputs
An algorithm is a well-defined computational procedure consisting of a sequence of instructions that solves a problem. Algorithms are precursors to program development – just the representation of logic while data structure is added during implementation to form a program. Programs must be written in the structure of some programming language – with correct syntax. Properties of well-defined algorithms:
A general solution to the problem in a finite number of steps
Clearly defined and unambiguous
Flow of control from one process to another (must be clear and logical)
Algorithms may be represented as:
Narrative - This is the use of natural language and natural language rules to construct sentences and paragraphs which describe the actions to take. Advantages include: o it can be applied outside of computing, o It can be understood by most persons o It requires no special training to construct The disadvantages of a narrative are that: o it can be too verbose (too wordy)
o It can be context-sensitive (interpretation varies depending on person’s background and experience)
Flowcharts – This is a diagrammatic representation of the sequence of steps needed to perform a task. Advantages include: o it is easy to understand by persons at all levels because of the visual nature o easily seen flow of logic Disadvantages include: o They can become large and unwieldy when the programs are long and complex o When alterations are required the flowchart will have to be completely redrawn. o Reproduction: As the flowchart symbols cannot be typed, production of flowcharts becomes a complex exercise.
Pseudocode – This is a compact and informal high-level description of a computer programming algorithm that uses the structural conventions of some programming language, but is intended for human reading rather than machine reading. Advantages include: o independent of a particular language so programmers of different languages can all understand it o programmers do not have to worry about syntax o Lay people can help to determine the validity of the logic because it is not that difficult to understand
The disadvantages of pseudocode are that o It is very detailed and so requires a high level of concentration to determine the overall logic o The loose standards means that one solution may be depicted in several different ways by different persons
Control structures include:
Sequence – one statement follows another and they are executed in that order
Selection – the execution of a statement(s) depend on whether previous conditions have or have not been satisfied
Iteration or looping – a statement or section of statements is repeated once some condition is valid or for a specified number of times. These may be condition-controlled or counter-controlled.
A programming language is a set of words, abbreviations and symbols that enables a programmer to communicate instructions to a computer. Stages in program development include:
Analysing requirements
Designing a solution
Validating the design
Implementing the solution
Testing
Documenting (global and internal comments)
A programming paradigm refers to a way of conceptualizing and structuring the tasks a computer performs. Programming paradigms include:
PROCEDURAL o Programs are conceptualized as a series of steps that indicate how the problem must be solved o Include many first, second and third-generational languages e.g. COBOL, C, Fortran o Suitable for problems easily solved by linear, step-by-step algorithms such as transaction processing and problems in mathematics and science especially those which are largely number crunching o Procedural languages run quickly and use system resources efficiently o Not suitable for unstructured problems or those with very complex algorithms as the order is crucial, making it unsuitable for some problems
OBJECT-ORIENTED o The solution for a problem can be visualised in terms of objects (representing abstract or real-world entities) that interact with each other. Objects comprise methods (procedures – what it can do) and properties (what it knows – data). o Includes C+ + and Java o Suitable for a wide range of problems; once the problem can be envisioned as having objects which pass messages back and forth
o Helps solutions to be easily visualised as the paradigm is similar to how humans see the world; encapsulation and inheritance are great advantages o Strong base classes must be developed to support upgrades and meet needs of the application; quite a bit of memory and processing resources are required
FUNCTIONAL o Emphasises the evaluation of expressions rather than the execution of commands o The modular approach is used whereby larger problems are subdivided into smaller problems and a single solution is provided o Includes LISP, Scheme and Haskell o The high level of abstraction reduces the chances of committing may types of errors; relatively easy to develop and maintain very large programs; functions are reusable o Not suitable for problems with many variables; and errors are hard to find in very large programs
DECLARATIVE OR LOGICAL o The problem is described using a set of facts and rules but no solution is specified. o Includes Prolog and SQL o Suited for problems relating to words and concepts instead of numbers and calculations e.g. artificial intelligence applications and database queries o Offers flexibility when querying facts and rules; allows descriptions of problems using words o Has minimum input and output capabilities; not commonly used for production applications; may be time consuming
Validation aims to check that data is reasonable, sensible, complete and within set boundaries. Verification aims to check that the data entered is the same as that on the source document.
