Study Unit 4 computer systems and data communication

Wireless Network Configurations

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Wireless Network Configurations

Wireless networks can be configured in an ad hoc/peer-to-peer arrangement or as a local area network.

Ad Hoc/Peer-to-Peer Configuration

This is the most basic wireless network configuration. It relies on the wireless network adapters installed in the computers that are communicating with each other. A computer within range of the transmitting computer can connect to it. However, if a number of computers are networked in this way, they must remain within range of each other. Even though this configuration has no real administration overhead, it should only be a consideration for very small installations.

The Internet

What is the Internet?

The Internet which is also known as the Net is simply a network of networks. It is a world wide computer network that interconnects computer networks across countries.

A network is a group of computers that are connected so that they can share information. The computers are linked together through high speed telephone wires, satellite and any other telecommunication system such as cable networks. All computers on the Internet communicate with one another using the Transmission Control Protocol/Internet Protocol suite, which is commonly abbreviated to TCP/IP.

As a network of networks, the Internet allows people on one network to share information with people on another network that may be thousands of miles away.
Through the Internet, one has access to a wide variety of services which include :

  • vast information resources,

  • interactive collaboration tools,

  • multimedia displays,

  • real-time broadcasting,

  • shopping opportunities,

  • and much more.

These services are available through the:

  • World Wide Web,

  • electronic mail (email),

  • file-transfer between any two computers and,

  • remote access to a computer connected to the Internet.

What is needed to connect to the Internet

The minimum set of requirements to connect to the Internet is: a computer attached to an Internet entry point (a service provider) via a telecommunication link such as the telephone line and a modem. These are discussed in detail below.

Internet Service Providers

An Internet Service Provider (ISP) is a company that gives you access to the Internet. In Zimbabwe the common ISPs are ComOne, ZARNet, AfricaOnline, Ecoweb, ZOL , PowerTEL and many others. You sign up for an Internet access account through your selected ISP. Once you sign up for a dial-up account with an ISP, you will be able to communicate through the Internet and use the services offered, such as email and Internet access. Your ISPs can also provide you with numerous other Internet related services, such as domain name registration and website hosting.


When you are connecting through a telephone link, a modem is required. The modem must be connected to a telephone line to dial up your ISP’s computer network. A modem (MODulator - DEModulator) is a device that translates digital (numerical) signals from your computer into analogue signal (sounds) that are acceptable for an ordinary telephone line. A modem could be internal, that is, attached on the computer’s motherboard or connected external through a communication port on your computer.
To connect to the Internet using a dial-up connection you need a modem with a speed of 56 Kbps modems, which is the maximum for an ordinary telephone line. The speed at which data circulates through the modem and the telephone line is called bandwidth. The first modems had very low bandwidth of 300 to 1200 bit per second (bps). Today, even 14.4 Kbps (kilobit per second) and 28.8 Kbps modems have become obsolete.

Telecommunication link

A telecommunication link such as the telephone, satellite, fibre optics is required for connecting to the Internet. For a dial-up connection, a telephone link is required. When you dial to link your computer to the ISP network, your computer is connected to the Internet. As with ISP, your telephone services provider will offer many different plans and charging systems from flat rates to blocks of time. You must find the plan that works best for you according to prices that are offered and your specific needs.

It is always better to connect to the Internet on a direct telephone line through an automatic connection system because the quality of the line is very important. However, some technical solutions can correct mistakes and remove noise and disturbances. When the Internet entry point is in your local area, you will not need to pay for an intercity or trunk call, but for a local call. In Zimbabwe we dial 041 as the local call to connect to the Internet. This Internet connection will provide you with access to the entire world through your local connection. Please note that you are responsible for paying the telephone bill for the time you will be connected to the Internet.

Other types of telephone connection are dedicated lines, and the Integrated Services Digital Network (ISDN)

Dedicated lines

A dedicated line is a telecommunication path between two points that is available 24 hours a day for use by a designated user. A dedicated line is rented from a telephone company, in which case it is called a leased line. Thus unlike dial-up lines, it is not shared in common among multiple users. In this type of connection, you will pay the agreed rate to ISP, but you do not pay additional costs for the time spent while surfing the Internet. Such lines are ideal for schools and colleges where the Internet is need throughout the day.

Integrated Services Digital Network (ISDN)

Using an Integrated Services Digital Network (ISDN) adapter, instead of a conventional modem allows the transmission of data on an ordinary telephone wire at a much higher speed. When you connect using an ISDN adapter in place of a modem, you can access highly graphic webpages with easy and at a fast speed of up to 128 Kbps.
This new technology is not readly available in many developing countries. Since ISDN requires adapters at both ends of the transmission, your access provider also needs an ISDN adapter. So before you make the decision to install an ISDN adaptor you must check if your ISP has one. In some countries, ISDN is available from phone companies in urban areas.

The web browser

In addition to the things listed above, there are a number of pieces of software that works together to connect us to the Internet. One such software is the Internet browser. The browser helps us to locate websites and allows us to maneuver around or surf the World Wide Web as we view web pages. The two most frequently used graphic browsers are Microsoft's Internet Explorer, and America Online (AOL)'s Netscape Navigator. Before these graphic browsers were in use, Mosaic and Lynx were the most popular browser and these are still available for text browsing.

Internet Services

On the Internet we have access to a wide variety of services. In this section were are going to discuss, a few of these services, namely, the World Wide Web (WWW), electronic mail (e-mail), file transfer protocol (FTP) and UseNet news.
Electronic Mail

Electronic mail (e-mail) refers to the sending of digitally encoded messages through the network. Electronic mail is one of the fastest and easiest ways of sending electronic messages from one person to another or to a group. Email systems enable us to conveniently and quickly send a message to many people at one time. Messages sent through e-mail can arrive within a matter of seconds. Although email is used primarily for sending written messages, we can also send and receive pictures, sounds and video images as attachments to the text message. These files are referred to as MIME attachments. MIME stands for Multimedia Internet Mail Extension. This technique was developed to help e-mail software handle a variety of file types. For example, a document created in Microsoft Word can be attached to an e-mail message and retrieved by the recipient with the appropriate e-mail program.

They are basically two types of e-mail accounts, these are, the one we can be given by our Internet Service Provider (ISP) and the one we can get free from the Internet. The email account we can obtain from the ISP is some times called the computer-based account. Computer based accounts have the advantage that students can downloads all their messages to read and respond to them offline. That is when they are not connected to the Internet. Students can only connect to download or post their messages. This saves on the telephone bill if the connection is a dial-up connection. The Internet based email account is sometimes known as web-based account. Web based email accounts are usually free of charge and they are available from a number of providers on the Internet. These include yahoo mail, Hotmail, Gmail and many others. The major advantage of web-based mail is that students can easily gain access from any computer with Internet access.
The World Wide Web

The World Wide Word (WWW) or simply the Web is another commonly used Internet service. The World Wide Web is a system of Internet servers that supports hypertext to access several Internet protocols on a single interface. It provides Internet users with a uniform and convenient means of accessing a wide variety of resources including pictures, text, sound and video, available on the Internet. It provides a vast array of experiences including multimedia presentations, real-time collaboration, interactive pages, radio and television broadcasts. Both the teacher and the learner can retrieve documents, view images, animations and videos, listen to sound files, speak and hear voices through the Web.

The information is found on files called web pages or web sites. A web site is a set of interlinked files on a web server computer. Each website has an address, known as a “URL,” that locates it on the internet. Websites are typically organized around a “home page” that serves as the entry point to other pages. Websites can present information in words, pictures and sounds, and they can enable us to exchange information with our students.
A web page is written in a special programming language called hypertext mark up language (HTML) and its filename ends with file extension html. Hypertext is basically a document containing words that connect to other documents. The principle of hypertext is that one text or web page can refer to or point to another web page, either on the same website or another website somewhere else in the world. Thus it is easy for the web pages to link to another web page on the same computer or different computers, anywhere on the Internet. The pages are linked by special links called a hyperlinks. The hyperlink can be taken as a method of instant cross-referencing of information on web. A hyperlink is shown by a coloured and underlined stretch of text or graphic image where the shape of the cursor changes to a pointing hand. These words are called links and are selectable by the user. In some cases hyperlinks take the form of buttons, images, or portions of images that are clickable. A single hypertext document can contain links to many documents. When you select one of these words or phrases, you will be transferred to the site or page that is linked by the word or phrase.

How to Access the World Wide Web

For you to access the World Wide Web a Web browser is required. A browser is a software program that allows users to access and navigate the World Wide Web. There are two types of browsers, namely graphical and text browsers. These are explained in detail below.
Text Browsers

Text browsers, such as Lynx provide access to the Web in text-only mode. Navigation is accomplished by highlighting emphasized words on the screen with the up and down arrow keys, and then pressing the forward arrow or the Enter key to follow the link. Today, these browsers are fast loosing their popularity due to the development of more user friendly graphical browsers.

Graphical Browsers

A graphical browser such as Internet explorer, Netscape Navigator, Mozilla and opera, enable us to retrieve text, images, audio and video. These browsers are available for Windows, Apple, Linux and other operating systems. Navigation is accomplished by pointing and clicking with a mouse on highlighted words and graphics.

Browser buttons

Address bar

Location on the browser where one enters addresses to web sites. The address bar is usually located on the top of the screen and it written “address.”


Clicking this button brings you back to a previous screen. The back button is located in the upper left hand corner of the screen.


Clicking on the “Forward” button brings you to a page that you viewed earlier


Clicking on “Home” on the top of the screen brings you to the home location to which the computer is set. Computers can be and are set to open to different Web site addresses.


Clicking on “Refresh” reloads an expired page or a page that has timed out.


Clicking this button stops the computer from loading a new page.

Scroll bar

The vertical gray space on the right and the horizontal gray space on bottom of the browser screen allows you to view parts of a Web page that do not fit inside the screen. When you cannot see the entire Web page, use the small box or the small arrows to move the page up and down, left and right.


Refers to the beginning page of a Web site. This page will link to other information found within the Web site as well as outside of the Web site.

A Note on Clicking


Use one quick (left) mouse click to open up a link or to darken (highlight) the address bar to type in a new web address.

Double clicking

Use two quick (left) mouse clicks to open up a program on your screen (such as Microsoft Word, Internet Explorer, etc.). Programs are usually represented by symbols known as icons.

Drop down menu

Clicking on a drop down menu reveals links. These menus are recognized by a small downward pointing arrow


Links are found on nearly all Web sites and take you from one part of the Web site to another (usually referred to as another “page”). Links can also take you to a completely different Web site. Links may be text (often underlined and colored blue) or a picture.

When using a mouse, the arrow becomes a hand when it is placed over a link.


Telnet is one of the services available on the Internet. Telnet allows the user to log onto computers on the Internet and use online databases, library catalogs, chat services, and more. The major disadvantage of Telnet is that there are no graphics in Telnet sessions. The most common Internet based resources available through Telnet are library catalogs, although most catalogs are now migrating to the Web. As the Web gains more popularity, Telnet is less frequently used as a means of access to information on the Internet, thus why most library catalogues are now migrating to the web.
A Telnet program must be installed on your local computer and configured to your Web browser in order to work. To Telnet to a computer, you must know its address. The addresses may consist of words ( or numbers (

File Transfer Protocol (FTP)

FTP stands for File Transfer Protocol. This is both a program and a method used to transfer files between computers. FTP is used primarily as a tool to efficiently uploading and downloading files on the Internet. FTP sites contain books, articles, software, games, images, sounds, multimedia and many other forms of information. FTP transfers can also be performed on the World Wide Web without the need for special software. Programs such as WS_FTP for Windows can be used to conduct a file transfer. FTP files can also be retrieved via search engines such as FtpFind, with URL This option is easiest because one does not need to know FTP program commands. The Web browser is sufficient to carry out the process. In fact every time we download software from a Web site to our computer, we will be using FTP.

Study Unit




Businesses rely on information because it allows them to make decisions. Incorrect decisions can be fatal and reliable information is therefore of critical importance.

The output of information systems consists of information, which is made available to users who then base their decisions on it .This study unit will look at:

  • Who these users are

  • And why these users need the information that they need


  • External users

  • Internal users


  • Transaction processing systems

  • Management information systems

  • Decision support systems

  • Executive information systems

  • Expert information systems


They help an organisation to maintain an advantage over its competitors by offering new services to clients before competitors can and by improving the cost and quality of existing services.

  • Increasing use of the internet, e-mail, and e-commerce

  • Has also led to the development of new legislations to govern the use and conduct of users of these technologies

  • In the work environment , computers have led to the following

  • Reduced need to follow chain of command

  • Information overload

  • Retraining of staff

  • Closer business relationships

  • Working from home

  • Human computer interface

  • Effects of technology on the workforce


  • Information technologies have allowed people around the globe to be able to trade with each other any time of the day and year.

  • Business opportunities are now unlimited but they bring with them new risks and threats.


Read from ISSABE, Chapter 8 (para 8.5.5)

  • Study Unit

  • 1

Study unit



Because of the rapid developments in the field of information technology, it must be managed effectively. Management should be carefully plan hoe to handle the information systems.

Such a plan is called a strategy. An organisation that does not have an information systems strategy is like a rowing boat adrift a big ocean.

The information strategy

Information systems are critical for the success of many organisations and hence the need to have a well organised information management system in place. This need also stems from the following:

  • The high costs involved in acquiring and maintaining information systems

  • The increased levels of customer service due to the use of information systems

  • The achievement of competitive advantage

  • The improved quality of information that can impact on the quality of decisions taken by management.

The formulation of an information systems Plan

  • Strategic analysis using critical success factors

This involves analysis of small numbers of key and vital goals that are vital for the success of an organisation.

SWOT Analysis

An organisation must analyse its internal environment

Study unit




This study unit presents an overview of the main stages involved in the development of information systems. There are a number of ways by which an information system can be developed. The choice of a particular method depends on the specific characteristics of the development project such as

  • The size

  • Scope

  • Limitations

  • Time scale

  • And the user’s specifications

One of the more popular methods is the systems development life cycle (SDLC).This model is based on a logical step-by-step approach to system development

There are other strategies that an organisation could use if it doesn’t want to develop the new system on its own. These will be discussed later in the study unit as well.
Reasons why systems get obsolete or become outdated

  1. The rapidly changing technological environment

  2. Changing output needs of the information system

The Systems Development Life Cycle

The phrase “systems development” covers the development of computer systems from the initial idea through to the eventual installation of working systems

  • The development of particular system is carried out by a project team which will consist of:

  • Users

  • Managers

  • Data processing staff consisting of systems analysts, programmers and database analysts

All projects to develop information systems go through a number of stages known collectively as the Systems Development Life Cycle (SDLC).The SDLC is an example of a systems development methodology.

A methodology is simply a collection of stages, procedures and techniques to assist systems developers in the construction of new information systems. It is the segmenting of projects which allows managers to verify the successful completion of project phases before allocating resources to subsequent phases.

A disadvantage of this model is that it does not guarantee the optimal use of human resources, because each stage deends on the successful completion of the previous stage.It alsdo focuses primarily on project organisation, rather than meeting the users’ needs.

The stages in the SDLC and their respective end products are:

  1. Project Definition

The result is statement of scope and objectives

  1. Feasibility study

Result is the Feasibility report

  1. Systems Analysis

Result is a detailed requirements specifications report

  1. Systems Design

Result is Systems specification

  1. Programming

Result is a Program specifications and Program code

  1. Implementation

Result is a live system


  • What is involved at each stage of the SDLC

  • Why it is important to involve the user during each stage of the SDLC


There are disadvantages in using structured system analysis and design methods when developing information systems and for this reason one may choose to use alternative methods. The information system does not to be developed by the organisation itself.

Please read ISSABE, Chapter 10 ( Para 10.4) paying particular attention to the following:

  • Off the shelf software packages

  • Prototyping (modelling)

  • Application development tools

  • Software houses/ bureaus

  • End-user development

  • Outsourcing

  • Re-engineering of business processes

  • Joint applications development

  • Rapid applications development

Study unit


Information System Controls

An organisation’s protection of its information-based assets is now seen as an important and real challenge. The violation of privacy and the illegal use of information systems to commit crime or to bring about economic loss to a third party have a number of legal and financial implications. Most common threats that exist include:

  • Errors of omission at data input/entry

  • Fraud by theft

  • Disgruntled employees

  • Physical and infrastructure threats

  • Malicious hackers

  • Industrial espionage

  • Unauthorised and inappropriate use of information systems

  • Employee lack of know-how on use of information technologies.


Computer crime includes criminal activities of a traditional nature, such as theft, fraud, forgery and mischief. In summary the types of Computer Crimes are:

  • Fraud by computer manipulation

  • Computer forgery

  • Damage to or manifestation of computer data or programs

  • Unauthorised access to computer systems and services

  • Unauthorised reproduction of legally protected computer programs.

  • Introduction of malicious programmes/ viruses

  • Computer hacking


This refers to measures that are meant to reduce unauthorised access to, use and destruction of an organisation’s data and data resources.

Threats to security come from outside (external) and inside (internal) the organisation.

Securing data entails making sure that the computers are in the right environment, there are right software measures to reduce loss or theft of data.

Security of Equipment

This entails the need to look after the computer hardware well to avoid loss of data or the computers themselves. These include

  • Ventilation

A good room has to be adequately ventilated. If ventilation is poor the computer may over heat and thus fail to operate properly.

  • Power supply

Should be of the right voltage and supplied from safe socket outlets

  • Use of Uninterrupted Power Supplies (UPS)

  • Carpet

These are good dust absorbers. Fust interferes with the operation of electronic equipment.

  • Curtains

They reduce the amount of light an heat getting to the computer screens.

  • Lockable doors

  • Metal bars and shutters

This reduces unauthorised access

  • An alarm system

This may help warn of an intrusion

  • ID badges

They limit access to the room to authorised individuals only

  • Security guards

  • Attach computers permanently to the desks using clamps to avoid theft of the computers

  • Have all equipment serial numbers for use if equipment is stolen.

  • Have fire fighting systems in place to deal with any risks of fire to the equipment.

Security of Data

Data itself is at risk of accidental or deliberate loss and theft.

Accidental loss may occur this way

To reduce the risk of loss there is the use of back-up of data. Best way to keep backups is to make sure that a copy is kept on a different medium and in a different place.
Deliberate damage is loss of data by viruses or hackers.
Computer Virus

A virus is a harmful program that copies itself onto other programs and destroys them or interferes with their proper functioning. To reduce the risk of virus infections, the following may be effective:

  • Use anti-virus software

  • Use genuine software

  • Write protect all software programs

  • Make regular back-ups


A security policy should clearly state what controls need to be implanted to limit computer crime. This policy should be revised regularly to determine whether the organisation’s confidentiality and integrity are still protected.

Controls are usually categorized as:

  • Preventative

These are designed to prevent unauthorised or invalid data entries

  • Detective

These help to identify unauthorised or invalid entries

  • Corrective

These assist in recovering from unwanted occurrences

Typical control mechanisms that maybe included in such a policy are:

Application controls include policies and procedures associated with user activities and the automated controls designed into applications. Application controls are categorized as follows:

  • Input controls

These help ensure employees accurately input information, systems properly record input, and systems either reject or accept and record, input errors for later review and correction.

  • Database and file controls

  • Processing controls

They help ensure systems accurately process and record information and either reject, or process and record, errors for later review and correction. Processing includes merging files, modifying data, updating master files and performing file maintenance.

  • Output controls

They help ensure that systems securely maintain and properly distribute processed information.
Controls should be in place to address both batch and on-line environments. Standards should address procedures to ensure management appropriately approves and control overrides.
Please read ISSABE Chapter 11 ( Para 11.4-

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