CONCISE COMPUTER SCIENCE

TEXTBOOK FOR CHILDREN

BOOK III

BY:

WOLE ADEDOYIN

HISTORY OF COMPUTERS

Performance objectives

Pupils should be able to:

i. Identify early counting devices

ii. Identify early mechanical calculating devices

iii. Identify the landmarks in the transition of early

calculating devices to present day computers.

EARLY COUNTING DEVICES , COUNTING WITH

FINGERS, TOES, PEBBLES, STONES AND STICKS.

In the olden days, before the introduction or invention of

computers. Our forefathers were once using pebbles, stones,

sticks and fingers to count their products and commodities.

Also in the olden days, human being communicates only

through words, both written and spoken. In the ancient times

until about 150 years ago, messages and information were

either verbal or written system.

Getting a message to a distant recipient was often slow and

sometimes the message (or the messenger) got lost in the

process. As science and technology proceeded, scientists

developed devices as to help them calculate and

communicate faster over greater distances.

Traditional devices like Abacus and Calculator are traditional

calculating devices used for solving simple calculations in the

olden days.

GENERATION OF COMPUTER

The growth of computer can be divided into five distinct

generations. Each refers to the distinct technological break

through in the development of computers.

(i) First generation computer (1940-1958)

This generation was characterized by the use of vacuum

tubes or thermionic valves. These tubes, though the best

material the technology could offer at this time, made the

computers unnecessarily big, dissipated a lot of heat, costly,

very slow and unreliable when compared with computers of

later generations. They made use of Magnetic Drum as the

primary storage medium. Examples are EDSAC, EDVAC, and

UNIVAC 1 & II

(ii) Second generation computers (1959-1964)

The computers of this generation were designed with

electronic transistors. They proved more reliable, cost less,

faster and smaller in size. Similarly, the Magnetic Core

replaced the Magnetic Drum as the primary storage medium.

Examples are Boroughs 200series. Honey-well 800, IBM

7070, 7080, IBM 1600 series, UNIVAC III etc.

(iii) Third generation computers (1965-1970)

These are computer produced using the technology of the

middle 1960’s. They were designed using Integrated Circuits

(ICTs). With these ICs, hundreds of electrical components

were built into silicon Chip. The Magnetic Core and the Solid-

state remained the primary memory. They were faster, more

reliable, less expensive. and lighter in weight. IBM introduction

the IBM system/360 in 1964 and has ever remained in the

fore-front.

The use of integrated Circuits was later followed by Medium

Scale of Integration (MSI and large Scale of Integration of the

electrical components. These led to a further reduction in size,

reliability and overall manufacturing costs. These gave birth to

the microcomputers and minicomputers and the revolutionary

effect on the industry from the early 70s cannot be over-

emphasized.

(iv) Fourth generation computers (1971-1985)

This generation is characterized by the use of very large scale

integrated circuits (VLSICs) which mans many components in

very small space, and the use of bubble memories. This was

a thin line of demarcation between the third and the fourth

generations. This further led to reduction in the physical

components of the computer.

Through VSLIC, it was possible to build over 20, 00

components onto a small piece or a single silicon chip (about

the size of a finger tip). This technique led to the invention of

Microprocessors and hence the both of the pocket calculators

and digital watches.

(v) Fifth generation computer (1985-Date)

Many schools of thought classified the advent of the

Japanese industrial robots as a distinct generation. Hence the

fifth generation. This generation was characterized by the

advent of Artificial Intelligence (AI), Speech Processing,

Parallel Architecture, Pattern Recognition, Expert System, and

Multimedia System.

Artificial Intelligence is the ability of the computer exhibit

behaviors like an intelligent person. An Expert System, on the

other hand, is an application program that has the capability

of making judgments and decision like an expert in a

particular field of application. It is an interactive system that

pits users through question and answer sessions to clarify

issues and make recommendations. An example is in the field

of medicine, where a computer would prescribe like a doctor

after performing the needed diagnoses. By the middle of

1998, the American celebrated the debut of the Voice

Recognition System .

PHOTOGALLERY OF 2ND AN

3RD GENERATION OF COMPUTER

Lord Kelvin’s Tide Predictor

Differential Analyzer

Harmonic Analyzer

Hollerith tabulating machine

Leibniz Wheel

EARLY COUNTING DEVICES

Calculating Machine by Blaise Pascal

ENIAC Computer

Joseph Jacquard Loom

Difference Engine

EARLY COMPUTING DEVICES

Abacus

The abacus is an instrument used to perform arithmetic

calculations. Developed in ancient times, the abacus is still

used in China, Japan, and Korea.

Slide Rule

Prior to the invention of the hand-held calculator, the slide rule

was a standard tool for engineers and scientists. Operating on

the principle that all mathematical computations may be

carried out on sets of sliding scales, the device looks much

like a heavily calibrated ruler with a movable midsection. The

midsection, called the sliding center scales, is engraved with

fine lines to allow the user to align different logarithmic scales

rapidly and efficiently. Multiplication, addition, subtraction,

division, squaring, cubing, extracting roots, and more

complicated calculations were computed regularly by adept

users until well into the 1960s.

ENIAC

Philadelphia has long been a center of high technology.

ENIAC (Electronic Numerical Integrator And Computer), the

first fully electronic digital computer, was introduced at the

University of Pennsylvania in 1946 and remained in service

until 1955. ENIAC contained 18,000 vacuum tubes and

required manual rewiring to be programmed.

Early Vacuum Tube

DIAGRAMATICAL ILLUSTRATION OF A COMPUTER

SYSTEM

Classes of Computer

The followings are the 4 types of computers always found and

use in different working places.

1. Micro-computer

2. Mini Computer

3. Mainframe computer

4. Super computer

Micro- Computer:

This is the smallest type of computer and is generally

designed for a single user. Micro- computer gets name from

the tiny electronic component called the micro- processor

which does the processing, sorting, arranging and the

transformation of data into a useful information .

Micro computers are most often found in the office, hospital,

schools, home, banks, airports and supermarkets.

An ancient microcomputer

An Electronic Data Recorder

Mini Computer:

Mini computers are very big in size. They process and solve

complex tasks.

They do not have the complex processing power and memory

of the mainframe computers. They are bigger than micro-

computers. They are mostly found in banks, airports, hospital

and different organizations.

Computer Card Key Punch

Mainframe Computers:

These computers are very fast, they have a complex (large)

memory for storing and retrieving data and information. It

allow many users (people working on the computer) at the

same time. They are mostly used for performing complex

calculations by the research organizations, industries etc.

IBM System/360 Mainframe Computer

Supercomputer is the biggest of all. It processes multiple

amount of data and also uses multiple processors for solving

and carrying out its tasks.

Cm-5 Supercomputer

Cray Supercomputer

OUTPUT DEVICES

Performance Objectives

Pupils should be able to:

i. State the meaning of output devices

ii. Recognize a printer and monitor as

output devices

iii. State the uses of a monitor and

printer.

OUTPUT DEVICES

Output devices are machines through which the result of

processing is made available to the user.

Examples of output devices include : printer, plotter, monitor,

speaker, modem, webcam etc.

The two major popular output devices are: Monitors and

Printers.

The result gotten through the monitor is called Softcopy.

The result gotten through the printer is called Hardcopy

The result gotten through the speaker is called Voicecopy.0

USES / FUNCTIONS OF OUTPUT DEVICES

Monitor:

Displays the result on the screen. Another name for monitor is

VDU – Visual Display Unit.

USES/FUNCTIONS OF MONITOR

I. VDU display information on television like screen.

II. VDUs can typically display up to 32 lines of writing

(text up to 80 characters across the screen).

III. Information can be displayed on the VDUs on a

screen that has been divided into Windows, to

select particular items.

IV. Characters can be coloured, italicize, double height

and line spaced.

V. It is used for watching films.

VI. It is used for correction and editing errors.

OUTPUT

Getting processed information out of the computer is the job

of output devices. The computer can display the data on a

monitor screen of which there are several types.

1. Monochrome or White and Black

2. Colour

3. Flat Screen or Panel/LCD (Liquid Crystal Display) in

the case of laptop computers.

4. CRT (Cathode Ray Tube) in the case of desktop

computers.

You can also send data to a printer or plotter to make a paper

copy, use the modem to send the data over a phone line to

another computer or use any number of specialized output

devices like speakers, digital cameras, projectors etc.

PROCESSING

This part transforms data into a useful information. Once the

data is in a computer, it is processed by the processor and its

associated integrated circuit chips. Processors perform

calculations and manipulations necessary to transform data

into meaningful information. Also with the processor is the

memory, which is used for storing data and programs while

they are being used by the processor.

You have already seen that computers can receive data,

process it and display the results. However, computer can

laos store data for future use. The processing is carried out in

the Central Processing Unit (CPU) which is the heart and the

brain of any computer.

The CPU is made up of:

1. The Control Unit

2. The Memory Unit

3. The Arithmetic and Logical Unit (ALU)

STORAGE

This is the process of saving information inside and outside

the computer system. The computer system needs stored

programs and data to carry out the processing. Small

amounts of data are stored on Flash Disk, CD ROM. These

are called Backing Stores.

Where do you go if you want to keep the data into a

permanent place? That’s what storage devices are for.

Storage devices holds date permanently in the computer, so

that you can save it and retrieve it later. All computers use

disks to store data magnetically. Each type of disk is used by

its corresponding disk drive to read and write information.

Floppy disks are used for easy and portable storage.

Hard disks are used for more permanent storage of large

amounts of data and programs for fast access.

PRINTERS

Printers create paper copies called hardcopies of information

sent from the computer system. The type of printer used with

a particular computer system depends mainly upon the speed

of printing and the quality of print required.

Types of printers

Printers are divided into two

i. Impact Printer

ii. Non-impact printer

Impact Printer:

Strike the paper with pins. Impact printers are noisy when

printing and they allow multiple copies of documents to be

made by using carbon paper between the sheets of paper.

Non Impact Printer

This forms the image without striking the paper. It includes

desk or inkjet and Laser jet printers.

Examples of Impact printers: Dot Matrix Printer, Daisy Wheel

Printer, Chain Printer, Drum and Barrel printer.

Examples of Non Impact Printer: Thermal Printer, Inkjet

Printer, LaserJet Printer and Graph Plotter

An output from dot matrix

Dot matrix

Daisy Wheel Printer

SPEAKER

Speaker gives out sound from the computer system.

Speaker

USES/FUNCTIONS

i. Gives output from the computer in the form of

sound.

ii. Speakers’ control buttons can be used to high-low

or change the setting of sound effects.

PLOTTER

Plotter is an output device used for drawing and printing

graphical lines.

USES/FUNCTIONS

i. Plotters are used for drawing two or three

dimensional drawings as used in engineering

designs concept.

ii. It is also used for the production of hardcopies

(printouts) of pictures, drawings and graphs.

iii. Objects can be displayed in two dimensions or as a

solid object in three dimensions.

iv. A variety of colours and intensities can be achieved

depending on the number of points plotted.

v. Scaling and dimensions can be inserted by the

computer to produce a complete detailed plan of the

designed object.

vi. Plotter produces a drawing of the design, this might

be a graph, a line drawing or a picture.

Plotters

Drum plotter showing the different pens

The Flatbed plotter

COMPONENTS OF A SYSTEM UNIT II

Performance Objectives

At the end of the lesson pupils should be able to:

i. Identify the location of the disk drive

ii. Explain the meaning of disk drive

iii. List types of disk drives

iv. State the functions and uses of disk drive

v. State Dos and don’ts of using disk drives.

DISK DRIVES

Disk drives consist of floppy disk, CD ROM and Hard disk

drives.

TYPES OF DISK DRIVES

I. Floppy disk drive

II. CD ROM drive

III. Hard disk drive

USES OF DISK DRIVES

I. For storing information

II. For managing files and folders

III. For exploring files and directories

IV. For retrieving and saving files.

DOS OF DISK DRIVES

I. First eject the CD from the drive before shutting

down the system

II. Wipe the surface of the disk before injecting it into

the drive.

III. Keep the disk in a safe and warm place , preferably

in its jacket.

IV. Press the inject and eject button gently

DON’TS OF THE DISK DRIVES

I. Don not shut down the system if the disk is still in

the drive

II. Do not allow any damage disk into your disk drive

III. Do not allow any damage disk into your disk drive

IV. Do not expose the drive to water and dust.

V. Do not allow any unauthorized user to make use of

your disk drives.

STORAGE DEVICES

Storage devices are tools used for storing and saving

information inside and outside the computer system.

CLASSES OF TORAGE DEVICES

I. Internal storage devices

II. External storage devices

Internal storage devices : are devices used for saving data

into the computer system eg. Hard disk.

External Storage devices: are storage devices used for saving

data outside the computer system e.g CD Rom, Flash drive,

Floppy disk etc.

TYPES OF COMPUTER STORAGE DEVICES

i. Flash drive

This is an external storage device used for saving information

outside the computer system. It is measure in Megabyte and

Gigabyte. Flash drive is a removable storage device.

ii. Hard disk

This is an internal storage device used for saving data inside

the computer system. It is symbolized by C: . It is a non

removable storage device.

Tape Streamers

Video disks can store voices, graphs and pictures

iii. DVD

This is a data-only format, much like a CD Rom disk. It can

only read the content of DVD disk.

iv. CD ROM

CD Rom can hold large amounts of removable data and can

be mass-produced at a very low cost. The full meaning of CD

Rom is Compact disk read only memory.

Micro drives

THE FLOPPY DISKETTE

Pupils should be able to:

i. Identify a diskette

ii. Describe a diskette

iii. Mention types of diskettes

CARE OF DISKETTE

i. Do not expose the diskette to water and dust

ii. Always keep it in its jacket

iii. Keep in a warm place

iv. Always eject before shutting down the computer

system

v. Do not allow bad diskette into your diskette drive

Floppy disk drives also called diskettes are magnetic storage

media that are removable and easily transported from one

place to another. They are inserted into a floppy disk drive.

Floppy disk drives come in several sizes and storage

capabilities.

Two floppy disk types : 5.25 and 3.5. The 3.5 format is

considered superior, both because it stores more information

and because its more rugged. The 3.5 disks have plastic case

and sliding metal cover for the data window protect the disk

better and the locking write-protect tab is more durable and

convenient than the stickers you must place over the write –

protect notch of the 5.25 disk.

Floppy disk drives are needed to place software on your

computer and exchange data with other people. There are

currently two sizes of floppy disks: 51/4 inch and 31/2.

Family Size Diskette (Capacity in byte)

IBM 5.25 360K

IBM 5.25 1.2MB

IBM 3.5 720K

IBM 3.5 1.44MB

Mac 3.5 400K

SLOTTING 31/2 DISKETTE INTO CPU DISKETTE DRIVE

1. First check to make sure that there is no

floppy diskette in the drive.

2. Make sure the magnetic side of the

steel faces up

3. After this, slot in your diskette gently.

TO EJECT YOUR DISKETTE DRIVE

Underneath your floppy drive is a small button called diskette

eject button. It is the button you will press that will pull out

your diskette for you.

Note: Do not eject the button when the floppy drive light is on.

Wait until the light is off before you reject it.

Diffferences between computer and typewriter

A computer is completely electronic

Absence of electronic part s in typewriter

In computer functions are carried out with electronic

signals

A computer can hold and remember information for

future use

Typewriter cannot hold and remember information for

future use

A computer is programmable

Typewriter is not programmable

BINARY SYSTEM

Human data is a series of complex thoughts and ideas, but

computer data is nothing more than a series of electrical

signals. To convert human data into a form the computer can

understand , each number, letter, or any other input is

converted into a specific compbination of electrical signals in

binary forma