What is a computer

Week 1: Introduction to Computers

Course Outline:

  1. What is a computer?
  2. Different parts of a computer system
  3. Different types of computers
  4. Brief history of computers

Learning Objectives:

Upon completion of this course the student should be able to:

  1. Identify and describe different parts of a computer system (hardware devices for input, processing, storage, output, and communications)
  2. Differentiate between the operating system in a computer system and application software
  3. Distinguish four kinds of computers - microcomputer, minicomputer, mainframe, and supercomputer
  4. Relate the first, second, third and fourth generations of computers

1. What is a computer?

A computer can be defined as:

An electronic device that can follow instructions to accept input, process that input and output information.

  • The term computer is derived from the verb "to compute" which means to calculate. Primarily computer was designed to perform arithmetic calculations.
  • Today, computers are present in almost all spheres of human activities. Besides computing figures, computers can be used in communication in networks and the merging of computing and the telecommunication sectors has engendered a new discipline named the Information and Communication Technology, ICT.
  • The main advantage of using a computer is that it can solve complex problems in a very short time and its very often cost effective.

1. What is a computer?

1.1 System Unit

The system unit houses the basic electronics in the computer:

Motherboard: where all electronic devices are plugged.


Primary Storage

Memory (RAM /ROM)

Secondary Storage

(Floppy disks, hard disk, CD, Tape.)

Ports: enable connection with motherboard to external devices like a scanner

Peripherals: refer to all the other devices attached to computers that handle input and output

  • input devices include keyboard, mouse, digitizer, scanner,..
  • output device include monitor, printer, speakers,...

A brand is a product, service, or concept that is publicly distinguished from other products, services, or concepts so that it can be easily communicated and usually marketed. Examples of brand computers are HP and Compaq.

Clone computers are computers whereby the parts assembled are from different manufacturers and without a distinguishable name.

2. Different parts of a computer system






Generally in an Information System we can add also a fifth part called Procedures. An information system is similar to a computer system but more from an information perspective.

Procedures are in fact the rules or guidelines people follow when using software or hardware, and data. These procedures are documented in manuals written by computer specialists.

2. Different parts of a computer system

2.1 Hardware - Central Processing Unit (CPU)

  • The Central Processing Unit (CPU) is the essential component of a computer because it is the part that executes the programs and controls the operation of all hardware. It can be compared to the human brain in the nervous system.
  • Powerful computers may have several processors handling different tasks, although there will be need to be one central processing unit the flow of instructions and data through subsidiary processors.
  • Most Personal Computers are based on complex instruction set computing (CISC) chips that contain large instruction sets.
  • Reduced instruction set computers (RISC) processors use smaller instruction sets. This enables them to process instructions faster than the CISC processors.
  • RISC processors are found in Apple's Power PC as well as IBM and HP, workstations, minicomputers and mainframes.

2. Different parts of a computer system

2.1 Hardware-Memory

Memory are microchips made up of semiconductor.

Memory also called primary or main storage or Random Access Memory (RAM) holds data and program instructions for processing the data.

Read Only Memory (ROM) are microchips were data is kept permanently and cannot be erased.

Memory stores input for and output from the CPU as well as the instructions that are followed by the CPU.

The amount of memory stored is measured in bits, bytes, kbytes(kB ~103 bytes), Megabytes( MB ~ 106 bytes), Gigabytes(GB ~ 109 bytes), Terabytes(TB, 1012 bytes).

The amount of main memory (RAM) affect the performance of a computer because it is where programs are actually processed or executed. One method to speed up a computer system is to increase the amount of main memory.

Random Access Memory or RAM is the memory that the computer uses to temporarily store the information as it is being processed. The more information being processed the more RAM the computer need. When the program needs more than the RAM can provide, then the hard disk can be used as a temporary memory.

2. Different parts of a computer system

2.1 Hardware - Storage Devices

There are 2 types of storage devices:

  • Magnetic Storage Devices
  • Optical Storage Devices

Magnetic and Optical storage devices can further be divided into 2 categories:

  • Fixed: hard disks,....
  • Dismountable: floppy disks, CD ROM, Magnetic Tapes,..

The above-mentioned storage devices are secondary storage devices that hold data even if the computer is turned off. Computers can use several different media for storing both raw data and programs.

Storage media differ by the following:

  • storage capacity
  • speed of access
  • permanency of storage
  • mode of access (write, read, read only,..)
  • cost

Disk Size------------------Capacity Approximate printed 8.5 x 11 inch pages

3.5" Floppy High Density---1.44 MB 720

Hard Disk------------------80 GB Many ebooks

CD-------------------------650 MB A small library

DVD------------------------4.5 GB A feature length movie

2. Different parts of a computer system

2.1 Hardware - Magnetic Storage Devices

  • Diskettes (Floppy Disks)
  • Hard disks
  • High Capacity Diskettes

(Zip Drive)

  • Disk Cartridges
  • Magnetic Tapes
  • Mobile USB Disk

High capacity diskettes (also called zip drive) can hold data equivalent to hundreds of 1.44 MB 3 .5 inches CD.

Disks cartridges can be found in interchangeable magnetic disks whereby disks cartridges can be removed or added.

Magnetic tapes are used primarily for backup data and programs.

Mobile USB Disk or pent drive is magnetic disk medium around 128 MB that can be plugged in the Universal Serial Bus port of a PC. Its normally a plug n play device just like a keyboard.

2. Different parts of a computer system

2.1 Hardware - Optical Storage Devices

  • Compact Disk Read Only Memory - CD ROM
  • Digital Video Disk Read Only Memory - DVD ROM
  • CD Recordable - CD R
  • CD Rewritable - CD RW
  • PhotoCD

A CD ROM has a capacity of around 600 to 700 MB and more widely used as a secondary movable storage than diskettes.

A CD-R is a WORM (Write Once Read Many Times) storage different form CD-RW that can be erased hundred times.

DVDs are used mainly for recoding movies, with enhanced numerical audio and video quality.

PhotoCD is a Kodak standard for scanning and storing images. Every image on a Kodak PhotoCD is available in five resolutions, the highest of which is 2,000x3,000 pixels (Pro PhotoCD contains one extra resolution: 4,000x6,000 pixels).

2. Different parts of a computer system

2.2 Software

What is a software?

A software is a set of electronic instructions that tells the computer how to perform certain tasks.

A set of instructions is sometimes called a program

When a computer is using a particular program, it is said to be running or executing the program

The two most common types of software are the system software and the application software

Software are generally installed from diskettes or CD onto computers. Some software can also be installed via a remote computer on a network or simply via the Internet.

Some software are machine dependent, that is it cannot be installed on all computers. For example Windows XP for HP branded computers cannot be installed on clone computers.

Application software can run on a specific operating system, others are platform (name commonly used for operating system) independent, which means that they are compatible with different operating systems.

2. Different parts of a computer system

2.2 Software: Operating System

System software exist primarily for the computer itself, to help the computer perform specific tasks

One major type of system software is the Operating System

All computers require an Operating System

The Operating System tells the computer how to interact with the user and its own devices

Common OS include Microsoft Windows, Macintosh OS, IBM OS/2, UNIX.

  • The operating system controls the input and output the flow of information to and from the CPU. Much of this is done automatically by the system but it is possible to modify and control your system if you need to.
  • When you turn your computer on it first needs to load the operating system sometimes referred to a booting up. Basically the computer starts from scratch every time you turn the power on.
  • It checks all its components and will usually display a message if there is a problem. Once the system is loaded the users can start the application or program that they are going to use.
  • Most modern Operating Systems, like Windows and Macintosh OS, provide a graphical user interface (GUI). A GUI lets you control the system by using a mouse to click on graphical objects on the screen.

2. Different parts of a computer system

2.2 Software: Application Software

Application software can be described as an "end-user" software.

Applications programs are used for all purposes other than performing operating system choices or writing other programs.

Applications programs include:

Word processors, spreadsheets, graphics programs, statistics packages, database management system,

airline reservation software,.......

  • Ready application software available in the market are sometimes called software packages. For example, MS Office can be purchased by anyone and ready for use.
  • However, there exist also tailor made software, which are not for commercial purpose developed for specific use in organizations.
  • In order to develop application software developers and software engineers use high level programming languages like C language or Visual Basic .Net.

2. Different parts of a computer system

2.3 Computer Data

Data consists of unprocessed facts including text, numbers, images, audio and video.

Data is stored in files which are used by the computer

Common types of data files are:

  • Word Documents
  • Spreadsheets
  • Database files
  • Presentation files

Computer data store in files is coded, manipulated and stored by use of an exclusively two-state condition:

  • In English such two state forms of information can include yes/no, on/off, open/closed, hole/no hole
  • In simple electronic terms this two-state condition can be translated for the computer into "switch open/switch closed" meaning that "there is electricity passing through the circuit/there is no electricity passing through the circuit"

In computer terminology, this two state condition is represented in binary notation by the use of 1s(ones) and 0s(zeros).

Each binary digit is called a bit.

A group of 8 bits is called a byte.

All data used by the computer is coded with bits and bytes, which are understood by the computer microprocessors.

2. Different parts of a computer system

2.4 Users / People

People are end users who use the computers to make themselves more productive

People are the most important part of a computer system / Information system

Year 2000's is the people era in computing

Proper usage of computers is beneficial to the user

  • The views of end users are crucial when designing systems and application software. For this reason many software development companies involve users in their analysis and testing phases in the development of their systems so as to meet the demand of the end-users and therefore provide value to customers and produce quality systems.
  • Nowadays with the advent of relatively easy Internet access and wireless technologies a user can interact with multiple computer systems with mobile devices. The user is therefore the principal actor in modern computer systems.
  • Misuse of computers by users can sometimes cause havoc in organization. The attitude and skills of a computer user is important for proper running of an information system.

3. Different types of computers

There are 4 types of computers:

3.1 Supercomputers

3.2 Mainframes

3.3 Minicomputers

3.4 Microcomputers

  • Computers can be classified according to their processing speed and storage capacity.
  • Different types of computers require different Operating Systems.
  • In a network of computers, the computers providing services (for example sending emails) to other computers are called Servers, which are generally more powerful than the workstations or client machines. A server is a computer that provides services to other users and is not used as an individual's computer

3. Different types of computers

3.1 Supercomputers

  • Supercomputers are the most powerful computers. They are useful for solving very complex scientific calculations. These machines are very big in size and storage capacity.
  • Cray has been a synonym for supercomputer since the mid-1970s. It comes from the computer engineer and entrepreneur Seymour Cray, who designed significant parts of those eponymous computers and over 20 years founded several companies manufacturing and selling them.
  • Supercomputers are mainly used by government agencies, universities, and large business organizations. For example scientists use supercomputers to study the effects of global warming.
  • Nowadays, it is possible to interconnect many Personal Computers to obtain similar processing power as supercomputers, such systems are called Clusters.

3. Different types of computers

3.2 Mainframes

  • Mainframe computers are specially kept in separate wired and air conditioned rooms.
  • Mainframe computers are less powerful than supercomputers but they can support hundreds or even thousands of users, handling massive amount of inputs, outputs and storage.
  • Mainframe computers are used in large organization where users need access to shared data and programs. For example, the banks use mainframes to process information amount millions customers.

3. Different types of computers

3.3 Minicomputers

  • A minicomputer is a computer of a size intermediate between a microcomputer and a mainframe. Typically, minicomputers have been stand-alone computers (computer systems with attached terminals and other devices) sold to small and mid-size businesses for general business applications and to large enterprises for department-level operations.
  • In recent years, the minicomputer has evolved into the "mid-range server" and is part of a network. IBM's AS/400e is a good example
  • These machines are used for specific purposes. For example, minicomputers are found in manufacturing processes or sometimes in networking services such as the Internet servers for hosting web sites.

3. Different types of computers

3.4 Microcomputers

Microcomputers can be categorized into 3 types:

  • Microcomputers are the least powerful, but most widely used and fast growing type of computer.
  • Microcomputers are more commonly known as Personal Computers. The term "PC" is applied to IBM-PCs or compatible computers.
  • Notebook or laptops are portable with the same capabilities of a desktop PC.
  • Handheld PCs like PDAs( Personal Digital Assistant) lack the power of a notebook or a desktop PC, but offer features for users who need limited functions and small size. The advantage of handheld devices such as the PDAs or palmtops or PDA-phone is that they combine pen input, writing recognition, personal organizational, and communications capabilities in a very small package.

4. Brief History of Computers

The Abacus was first used by the Babylonians as an aid to simple arithmetic at sometime around 500 BC. The Chinese used a device to assist in performing mathematical calculation starting in about 600 BC

In 1622 William Oughtred develops the slide rule in England

In 1642 Blaise Pascal builds the first numerical calculating machine in Paris.

4. Brief History of Computers

1822: In England, Charles Babbage often referred as the inventor of computers, designs a Difference Engine to calculate logarithms, but the machine is never built.

1833: Charles Babbage designs the Analytical Machine that follows instructions from punched-cards. It is the first general purpose computer.

1842: Lady Ada Byron, Countess of Lovelace and daughter of Lord Byron, the poet, documents Babbage's work and writes programs for Babbage.

1906: Electronic Valve developed by Lee De Forest in America. Before this it would have been impossible to make digital electronic computers.

1941: Colossus computer contained 2400 vacuum tubes and was built by Dr Thomas Flowers at the Post Office Research laboratories in London. Used for code-breaking during WW II

4. Brief History of Computers

first generation computers 1943-1959

1943-1959: usually regarded as "first generation computers", based on valves and wire circuits.

1946: ENIAC (Electronic Numerical Integrator and Computer), with 18,000 vacuum tubes, is dedicated at the University of Pennsylvania. It was 8 by 100 feet and weighed 80 tons. It could do 5,000 additions and 360 multiplications per second.

1951: UNIVAC I (is installed at the Bureau of Census using a magnetic tape unit as a buffer memory

1952: EDVAC (Electronic Discrete Variable Computer) completed at the Institute for Advanced Study, Princeton, USA (by Von Neuman and others). First computer to use magnetic tape.

1953: Estimate that there are around 100 computers in the world

4. Brief History of Computers

second generation computers 1959-1964

1959 -1964: Computers build between 1959 and 1964 are often regarded as "second generation" computers, based on transistors and printed circuits- resulting in much smaller computers.

1964: IBM announces the System/360, the first family of compatible general-purpose computers, with modular design to allow for upgrades after purchase.

4. Brief History of Computers

third generation computers 1964-1972

1964 - 1972: Computers between 1964 and 1972 are often regarded as "third generation computers", they are based on the first integrated circuits - creating even smaller machines. Typical of such machines was the IBM 360 series mainframe, while smaller minicomputers begin to open up computing to smaller businesses.

1965: The first supercomputer, the Control Data CD6600, was developed

1971: First microprocessor, the 4004, developed by Marcian E. Hoff for Intel was released. It contains the equivalent of 2300 transistors and was a 4 bit processor. It is capable of around 60,000 interactions per second (0.06 MIPS), running at a clock rate of 108 kHz.

4. Brief History of Computers

fourth generation computers after 1972

1972: Computers built after this year are often called "fourth generation" computers, based on LSI (large scale integration) of circuits typically 500 or more component on a microchip. Later developments include VLSI (very large scale integration) of integrated circuits 5 years later- typically 10,000 components. Modern circuits contain million of components.

1974: MITS Altair 8800 designed by Ed Rodberst and Bill Yates, the first personal computer to be available commercially released by Micro Instrumentation Telemetry Systems.

1975: Microsoft is founded after Bill Gates and Paul Allen adapt and sell BASIC to MITS for the Altair PC

4. Brief History of Computers

fourth generation computers

1976: Apple Computer is founded and introduces the Apple II personal computer.

1981: IBM enters the personal computer market, creating a de facto standard.

MS DOS from Bill Gates was the main operating system for all IBM-PC

compatible computers until 1995 when Windows 1995 came into the picture.

There are different eras in computing history as follows:

  • 70's mainframe era
  • 80's: PC era
  • 90's: Network era
  • 2000's: People era

WK1: Summary

  • A computer is an electronic device comprising a system unit (Motherboard, CPU, Memory, Hard disk,..) and peripherals (input and output devices and other components external to the case). The 4 parts of a computer system are hardware, software, data and people. From information system point of view "procedures" is the fifth part and people is considered to be the most important part.
  • All computers require an operating system, which acts as interface between the hardware and the user. Application software is different from operating system in the sense that they are general purpose and use.
  • There are 4 types of computers: supercomputers, mainframes, minicomputers and microcomputers. They differ from each other in terms of processing power, storage capacity, size and purpose of use.
  • Computers using vacuum tubes were called the first generation, transistors and diodes the second, ICs the third, and those using microprocessors the fourth. Whereas previous computer generations had focused on increasing the number of logic elements in a single CPU, the fifth generation, it has for long believed to turn to massive numbers of CPUs for added performance.

WK1: Conclusion

In this first, lesson we have introduced the concept of a computer and briefly describe different parts and types of computers, and finally the different computer generations according to technology. The lesson has been divided into 4 parts 1. What is a computer? 2. Different parts of a computer 3. Different types of computers 4. Brief history of computers.

Students are expected to answer all the review questions and understand all the key terms.

In the forthcoming lesson we will discuss more about internal functioning of the system unit, mainly the CPU and the system board.

The practical session for this week is about Mail Merge using MS Word 2002.

Review Questions

Encircle the correct answer(s).

1. Which one of the following can be compared to the central pocessor of a computer system?



2. PDAs, Palmtops and notebooks are which types of computers

AMinicomputers CSupercomputers

BMicrocomputers DMidrange computers

3. Which of the following are secondary storage devices?

AOptical disksCFloppy Disks

BDVDs---------DAll of the above

4. The most important part of an information system is:



5. Microcomputer hardware consists of three basic categories of physical equipment:

Akeyboard, monitor, hard drive------------------Csystem unit, input/output, memory

Bsystem unit, input/output, secondary storage---DNone of the above

6. Which of the following is part of the system unit?


BFloppy disks--DNone of the above

7. There are four types of computers: supercomputers, mainframe, microcomputers, and:

Aindustrial computers--Cmid-sized computers

BMinicomputers---------DNone of the above

8. Which one of the following is a system software?

Adatabase management system--Coperating system

Bapplication software--------Dinformation system

9. The four common types of files are document files, worksheet files, database files, and:

Apresentation files--Cprogram files

Bdigital files-------DSystem files

10. _______ are widely used to store and transport data from one computer to another?

AHard disks----CCD-ROMs

BFloppy disks--DDVD-ROMs

11. Which of the following is not an example of an Operating System?

AMS DOS-----CWindows XP

BMS Access--DLinux

12. Programs designed specifically to address general-purpose applications and special-purpose applications are called:

Aapplication software--Coperating system

Bsystem software-------DNone of the above

13. For which computer did Bill Gates initaially sell the BASIC?



14. In which decade PCs were available on the market?



15. What unit of storage is used to represent one million bytes?



Key Terms

application software------output device


byte----------------------secondary storage devices

end user------------------Computer system

handheld devices----------data

mainframes----------------binary digit


microprocessor------------magnetic storage

operating system----------microcomputer

personal digital assistant--Information system

primary storage-----------minicomputer

random access memory------read only memory

supercomputers------------input device

system unit---------------optical storage


Computing Essentials by O'Leary Ed. 2004

Introduction to computers by Peter Norton

WK1- Lab: Mail Merge ( 2 hrs)

Application Letter

Industrial placement or work placement has been very often a preliminary step towards employment. The holidays between semesters is generally the appropriate period where students can spend their time in the industry gaining work experience. In this context, imagine you are looking for a placement in the IT companies in Mauritius to spend for some months. You will write a letter using Mail Merge to write to these companies to seek for an industrial placement. You will use the Internet to find addresses to write to.

1. Start Word and create a new blank document.

2. Click the Tools menu, then Letters and Mailings, and then click Mail Merge Wizard.

3. Leave the Letters option selected, and click the Next: Starting document link to begin the process.

4. Leave the Use the current document option button selected, and click the Next: Select recipients link.

5. Select the Type a new list option button, and then click the Create button.

6. Open your Web browser and connect to the Internet. Enter the URL ncb.intent.mu and press the Enter key or Go button or whatever your browser requires to go to that site.

7. Look for the list of IT companies. You may choose those which are in the field that you are interested in, for example if your wish to have a placement in the software development filed, then you may pick up only companies in software development.

8. Select some IT companies; look for the companies name and the company address. Copy the information to the New Address List dialog opened in the previous step.

9. Close the New Address List box, and when prompted, save the data source as Placement_Data.mdb (you can save it in Excel if you prefer, or some other format if necessary).

10. Click the Next: Write your letter link to begin creating the main document.

11. Insert the current date, and then insert the title, name, and address info merge field codes from the data source.

12. Write a salutation and insert the title and last name merge field codes.

13. Write a short letter expressing supporting your application for an industrial placement.

14. Sign your letter and save the main document as Placement_Main.doc.

15. Click the Next: Preview your letters link and examine the letters. Fix any problems that you see, and then click the Next: Complete the merge link.

16. Save your merged document as Placement_Merge.doc. Close the merge document, close the main document, and exit Word.

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