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This chapter introduces the student to what a computer is, classifies computers into different categories, compares the different classes of computers and also introduces the keyboard as a basic input device.


  1. Definition of a computer
  2. Classification of computers
  3. Physical size
  4. The way they process data
  5. By purpose
  6. By use
  7. Acquisition of Keyboard skills
  8. Layout of keyboard
  9. Summary
  10. Questions






Before we attempt to define a Computer, there are a number of associated terminologies that the learner needs to know beforehand. These are: Data, Information, and Programs.


Data is the name given to facts. For example, in a school, the number of students in a class, the number of teachers, names of students, the name of customers in a business.

Information is result from processed data. For example adding some numerical values like the numbers 14 and 17 into the computer will give you the result of 31. The later is information you required. Information can be defined as data computed into a more useful form than raw form.


Program is a series of instructions written in the language of the computer for them to obey and perform specific tasks as outlined by the instructions.


A Computer can therefore be defined as “an electronic machine that takes in data (facts) in the raw form, processes the data to give out in another form called information”.


When a computer is fed with data, it passes through four basic steps before the data can be displaced;

  1. Input Process – the user will type the data from say the keyboard (to be introduced later in the chapter) and the computer will accept the dame and store within it.
  2. Storage Process – the data that is fed into the computer at the same time is held, even during the time of processing and after processing; it can further be stored for further reference. These data are held in computer memory.
  3. Processing – the computer will manipulate the data held within it to a more useful form – results (information).
  4. Output Process – the user is given the information he desired.


The four basic processes can be summarized in the following way by looking at the same terms of information processing cycle.

Organizing data for processing – to get quality results (information) you must have quality data to start with. Unreliable original data generates unreliable results. If you give a computer garbage, you get garbage in return. Its called GIGO – Garbage In – Garbage Out.


Information Processing Cycle – Information Processing Cycle includes a series of steps for transforming data into meaningful information for people.


A cycle is defined as a sequence of activities performed in an order that it produces expected and meaningful results.


A Processing Cycle is repeated, it means, if the same resources are used in the same way, the same outcome will result. The standard cycle followed to process data and deliver information comprises of 4 major functions:

  1. Input Function  – the input function gathers and collects stored data items and enter them into the system for processing. Input can come from many sources, for example from files kept in the office, banking institutions and accounts.
  2. Storage Function – this function allows the user to store data being processed in the memory of the computer as well as to store the information for future use.
  3. Processing Function – the desired operation by the user is carried out on the data keyed in and stored in the memory so as to turn it into meaningful information.
  4. Output Function – the data stored is processed and then output into files, printed as hard copies or displayed on the screen for the user.


For any information processing system to run smoothly on a day-to-day basis, the processing
activities must be organized. A system has little work if it provides helpful information on one day and useless information the next day. Output should be useful the first time and every time for the system.




There are four basic ways by which computers can be classified:

  1. Physical size i.e how large the computer is.
  2. By the way they process data
  3. By purpose
  4. By use


  1. Physical Size

The following computer systems are categorized by how large they are:

  1. Monster Computer

Sometimes it is referred to as Super computers or Maxi computers. These are computer of enormous power and are very large in size. Its installation requires special floors to carry its weights and it also needs special plumbing to carry a fluid known as fluorocarbon needed to cool it.

One unique feature of maxi computers is that when you purchase it, the purchase price will include the services of 2 permanent engineers to maintain it forever. They are typically used for scientific research and military applications, petroleum engineering, nuclear physics and meteorology.

Examples of monster computers include CYBER and CRAY computers. For example, the whole globe needs only one monster computer to forecast weather at once.

  1. Mainframe Computers

    Mainframe computers are second in size to monster computers. These computers perform more data processing work than any other type of computers. For this reason they form a large portion of installation in most organization.

    As does the monster computers, mainframe computers also have some special requirements, for the reason, they are housed in special rooms brought about by the special power that they posses together with environmental control requirements.

    Mainframe computers can be used by more than one person at a time since they can support a large network of other computers organizations that employ mainframe computers alongside other computers are banks, government agencies, commercial and industrial agencies.

  2. Minicomputer

    Also called Medium sized computers. These computers compared to mainframe are smaller, slower and less expensive.

    A minicomputer has an advantage over the previous two in the sense that it does not have any special power or environmental control requirements. For this reason, the medium sized computer can always be located anywhere within the organization.

    Minicomputers can do the work that the mainframe does but on a small scale.


  3. Microcomputers

    Of the types of computers, microcomputers are the slowest. However, they counteract this disadvantage because they are easy to use and the cost of purchase is also low.

    A microcomputer gets its name from the fact that its main computing component, the microprocessor (to be introduced later) is located in one integrated circuit (IC) or what we call a Chip. Microcomputers fit nicely on desktops, for that reason they are sometimes known as Desktop Computers. They are also referred to as Personal Computers since many individuals purchase them for personal use.


    1. Type of data processed

    Classification of computers by the way they process data falls into 2 main types with the third being a combination of the two:

    (i) Analog and  (ii) Digital Computers

    (iii) Hybrid

    1. Analog Computers

    These computers process data that vary continuously, for example variations in temperature, amount of current flowing through an electrical conductor and so on. The flow of such data is in the form of wave like movement i.e. not predictable. Such computers are used for a wide variety of industrial and scientific applications that require the processing of data that are measured continuously.

    In conclusion, we say that analog computers measure things.

  4. Digital Computers

    As opposed to analog computers, these type count things. Data passed to a digital computer is usually operated on in steps i.e. form of discrete numbers, 0, 1, 2, 3, (a discrete operation). It is like counting on one’s fingers (1, 2, 3, 4…). Most computers in use today are digital. This is because there are more counting applications than there are applications than there are applications that require continuous measurements.

  5. Hybrid Computers

    These computers possess features of both digital and analog computers meaning both counting and measurement operations in one computer.


    1. By Purpose

      Classification by purpose falls into 2 categories:

    1. Special Purpose Computers

    These are computers that are single task oriented. In other words, they are designed to solve only a particular type of problem. Examples include embedded computers in our common digital watches.

    1. General Purpose Computers

    These are computers that can perform a vast number of operations or solve problems of different varieties. Most of the computers in use today are general purpose. However, it is wise to note that general-purpose computers can always be adapted with special programs to do a job specified hence becoming special purpose computer.

    1. Embedded Computers

    These are computers attached to other computers that help in operating them. E.g. computers embedded in lifts, petrol pumps, digital watches and so on.


    1. By Use

    It is worthy noting that we categorize these computers according to what it is used for and when it is used. Under this category, the list is endless. For this reason we will limit ourselves to only five main types.



    1. Personal Computers or Desktop Computers

    These are also known as Microcomputers. They get their name from the fact that they fit nicely on the desktop. They can also be used on the desk in the office environment or for personal use at home.

    1. Home based Computers

    These computers are those designed to be used at home. An individual may install only games program in it or a word processor to enable them write letters, still some would install accounting packages to enable them budget and control their finances at home.

    1. Lap top Computers

    These computers get their name from the fact that you can place them on your laps while using. They are very small computers that have the structure of a briefcase i.e. you open and close the same way. These have a keyboard attached to them and a flat screen together with a mouse ball and chargeable batteries. This means that you can use them in the rural areas where the is no electricity.

    Laptop computers also have ports (small slots) through which you can attach an external keyboard, mouse or external drive like drive A:.




    There are many ways to enter data into the computer. However, keyboard still remains the predominant input device for the many users.

    A computers keyboard is used much like a typewriter keyboard. A keyboard has alphabetic, numeric, and special characters found on a typewriter. The only difference is that data keyed in, is recorded in the computer systems’ data coding scheme and is stored in the memory. The traditional format of a computer or terminal keyboard follows the organization prescribed by the typewriter keyboard. This is known as QWENTY keyboard because of the sequence of the six letters on the upper left corner of the alphabet position of the typewriter keyboard.


    1. Layout of Keyboard and Functions of Keys

    A typical keyboard takes the form of a normal typewriter keyboard. A keyboard usually has standard keys; that is letters of the alphabet plus special characters e.g. ?, ‘, @ e.t.c.

    In addition to the standard keys, one finds a numeric keypad which is essential for applications that require entry of large amounts of numerical information.

    Image From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.comImage From EcoleBooks.comFunction Keys are identified as F1 through F12, they can be programmed to ease the work of frequently used operations. Cursor control keys of direction keys ( ) the ones with arrows, move the cursor on the CRT (screen).

    Other special keys include: Delete keys and backspace keys which deletes characters. Delete key deletes a character that is in front of the cursor whereas backspace key delete characters before the cursor. Insert key will insert characters from text. Others e.g home key will take you to the top of the document and end key to the end of the document.

    Computer keyboard employ one or more control keys. Control works just like the shift key on a keyboard in that they cause other keys to perform functions different from their normal operations. Example, if you hold shift key down and press the letter “e”, you get a different character “E”. Holding down the control key while you press any of the other keys causes still another character to be sent to memory.

    Like the control keys, the escape key is used to cause other keys to perform special functions. Unlike the control keys, however, it is not held down while pressing another key. Once sending a signal to the computer system, for that purpose. If you press another key following Escape, it will cause the computer to execute a function established by the program in use.


    Image From EcoleBooks.comFig. 1.3.1 Layout of the Keyboard



















    1. SUMMARY


  • A computer is a device that takes data in one form and processes it to give out in another form called information.


  • Data is the name given to facts.


  • Information is processed data.


  • Program is a set of instructions written in the language of the computer indicating what the computer is to perform.


  • 4 basic functions of a computer: Input, Storage, Processing and Output.


  • Computers can be classified by: Size, The way they process data, By Purpose and by use.


  • Typical keyboard is the same as a typewriter keyboard, has: standard keys, Numeric Keypad, Function keys, Cursor Control keys or Direction keys, Control Keys, Alternate keys, Escape keys e.t.c.














  1. Define a Computer.


  1. Differentiate between Data and Information.


  1. What is a Computer Program.


  1. What are the 4 basic functions a Computer will perform on data.


  1. Discuss in detail how computers can be classified.


  1. Discuss the layout of a typical keyboard and functions of the different keys.




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EcoleBooks | Computer Studies Form 1 Notes : CHAPTER 1 - INTRODUCTION TO COMPUTERS


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