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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