INTRODUCTION TO INFORMATION AND COMMUNICATION
TECHNOLOGY(GST 115)
Supplementary Lecture Note 1
Afe Babalola University, Ado-Ekiti, Nigeria
Lecturer : Oguntimilehin A
THE COMPUTER SYSTEM
Computer is a programmable electronic device which accepts, processes, retrieves,
stores data and generates output (information) reports with high speed and accuracy.
PARTS OF COMPUTER
Computer system has four essential parts, they are (i) Monitor (ii) Central Processing Unit
(CPU) (iii) Key board and (iv) Mouse.
Central
Processing
Unit
Mouse
Monitor
Key board
MONITOR:- Monitor is also called the visual display unit (VDU)or Cathode Ray
Tube (CRT). It looks like television in shape. It displays input and output information. When
you type your name using the keyboard, you see it on the monitor. Black and white monitor
is called monochrome while the coloured monitor is simply called colour monitor. Monitor
are of different sizes.12”, 14”, 15”, 17”, 19”, 21”, etc. (12” means 12inch) Liquid Crystal
Display (LCD) technology is used in flat monitors
CENTRAL PROCESSING UNIT (CPU):- CPU is also called system unit. This is
the nerve center of a computer system. It is the place were processing is done. It is the most
essential part of the computer system. No CPU means no computer. CPU alone can work on
its own while other parts cannot work without the CPU. The CPU with flat casing is called
desktop case system unit, while the tall casing is called Tower case system unit. CPU is
called the brain of a computer system
KEY BOARD:This is one of the mostly used input devices. It allows data to
be keyed directly into the CPU from the key terminals. The computer keyboard resembles the
typewrite keys but different form it in many ways. Some keyboards have functions that can
perform the function of a mouse. The first key on keyboard is the Escape key. It is used to
terminate or stop the computer from doing what it is currently doing.
HISTORY OF COMPUTER
The term „computer‟ is the outcome of simple tools for counting in the olden days,
and even up today. These simple tools are called early aids to counting.
Early aids to counting
The early aids to counting include:
Fingers, beads, stones or pebbles, sticks and so on.
ABACUS:- The next idea was to use coloured beads held on a string. The Chinese used this
method to count. The beads were threaded on line of wire frame. The frame is divided by a
cross number so that each row of beads has a sector. The sector may have one bead up and
six beads below and another sector with four or sometime, five beads. The bead on the first
line counted the units, the beads on the second wire counted the tens. The beads on the third
wire counted the hundreds, the fourth wire counted the thousands and so on. By moving the
beads back and forth along the wire, numbers could be added and subtracted. This device was
called ABACUS.
NAPIER’S RODS
The Napier‟s rod was developed in 1617 by a Scottish mathematician and politician.
The Napier‟s rod was constructed from stripes of wood and bone. Mechanical multiplication,
division and taking squre roots of large numbers were done with the use of Napier‟s rod. He
also published the logarithmic tables called Nepearian logarithms.
THE SLIDE RULE
The development of slide rule was a further development or improvement on
logarithms. This was conceived by Rev. William Oughtred. The slide rule which behaved like
analogue computer, performed multiplication and division by addition and subtraction of log
tables
PASCAL’S ADDING MACHINE (PASCALINE)
Blaise Pascal 1642 in France invented a machine that could do both addition and
subtraction. The machine had wheels and teeth. The first wheel counted unit, second tens,
third hundreds and so on. Every time, the first wheel made a complete turn, the second wheel
moved one position. Ten turns on the first wheel caused one complete turn on the second
wheel.
One hundred turns on the first wheel caused ten turns on the second wheel and one
complete turn on the third wheel. By looking at the position of each wheel, you can read a
number from them. Examples nowadays are used in wall clock, fuel and electric maters. By
moving the wheels forward you add, and when wheels are moved backward, you subtract.
Pascaline was built when Pascal was only 19 years old to help his father a tax collector for
the French Government. Programming language „Pascal‟ was named after him in his honour.
LEIBNIZ CALCULATING MACHINE
The great German Mathematician Baron Gottfried Leibniz (1646-1671) built another
mechanical machine that could multiply and divide as well. He used pascal‟s ideas to create
this. This device could then add, subtract, multiply, divide and calculate square roots
JOSEPH JACQUARD PUNCHED CARDS
In the early 19th century French inventor Joseph-Marie Jacquard devised a specialized
type of computer, a silk loom. Jacquard‟s loom used punched card to program patterns that
helped the loom create woven fabric. Although Jacquard was rewarded and admired by
French Emperor Napoleon I for his work, he fled for his life from city of Lyon pursued by
weavers who feared their jobs were in jeopardy due to jacquard‟s invention. The loom
prevailed, however. When jacquard died, more than 30,000 of his looms existed in Lyon. The
looms are still in use today especially in the manufacture of fine furniture fabrics. The first
punched card was thus invented by jacquard
CHARLES BARBAGE’S DIFFERENCE ENGINE
Another early mechanical computer was the difference engine, designed in the early
1020s by British mathematician and scientist Charles Babbage. Although never completed by
Babbage. The difference engine was intended to be a machine with a 20-decimal capacity
that could solve mathematical problems. Babbage also made plans for another machine, the
analytical engine, considered the mechanical precursor of the modern computer. The
Analytical engine was designed to perform all arithmetic operations efficiently; however;
Babbage‟s lack of political skills kept him from obtaining the approval and funds to build it.
Augusta Ada Byron was a personal friend and student of Babbage. She was one of
only a few woman mathematician of her time. she prepared extensive notes concerning
Babbage‟s ideas and the Analytical Engine. Programming language (Ada) was named in
honour of her for her conceptual programs for the machine. Although the Analytical Engine
was never built, its key concepts, such as the capacity to store instructions, the use of
punched cards as a primitive memory, and the ability to print, can be found in many modern
computers.
HOLLERITH’S MACHINE
Herman Hollerith (1860-1929), American inventor, born in Buffalo, New York, and
educated at Columbia University, who devised a system of encoding on cards through a
series of punched holes. This system proved useful in statistical work and was important in
the development of the digital computer. Hollerith‟s machine, used in the 1890 U.S. census,
“read” the cards by passing them through electrical contacts. Closed circuits which indicated
hole positions, could then be selected and counted. His Tabulating machine company (1896)
was a predecessor to the International Business Machine Corporation (IBM)
TURING MACHINE
In 1936 British mathematician Alan Turing proposed the idea of a machine that could
process equations without human direction. The machine (now known as a Turing machine)
resembled an automatic typewriter that used symbols for math and logic instead of letters.
Turing intended the device to be a “universal machine” that could be used to duplicate or
represent the function of any other existing machine. Turing‟s machine was the theoretical
precursor to the modern digital computer. The Turing machine model is used by modern
computation theorists
MODERN COMPUTER
The threat of war speeds up technology, and computer technology has always obeyed the
rule. The first completely automatic digital computer was invented by Dr Howard Aiken of
Harvard University. It was called mark 1. Alken began work on it in 1937 and completed it
with US Navy financing it in 1944. Mark 1 was very big and it could not store information
internally. Programming was done by a punched paper tape fed into the machine. Its internal
operations were performed electronically, but its arithmetic counters were mechanical.
Therefore it was not an electronic computer, in fact it was more closely resemble Sir
Babbage‟s Analytical Engine. The first electronic computer for general purpose use was
Electronic Numeric Integrator and Calculator (ENIAC) (1945). Credit for the next great
innovation in computer technology goes to the mathematical genius John Von Neuman, who,
in a paper written in 1945 with collaborators at the institution for Advanced Studies presented
two basic ideas one (Rediscovering and extending Atanasoft‟s ideas), that the binary number
system be built into computers. This replacing the decimal of 0 to 9 with two digits 0 and 1.
The binary system corresponds to the „on‟ and „off‟ positions of all electronic computer
design.
The other (second) idea Von Neuman and his colleagues presented was the concept of
stored program. Computers had always been designed to store numbers in their memories but
early computers up to and including electronic computer such as ENIAC had to be totally
rebuilt (rewired) before they could start work on a new problem
A stored program computer is far more flexible. To begin with, certain basic circuits
and therefore basic operations are built in. Solving a new problem requires a new set of
instructions called a program to call up the basic operation in any desired order and perform
any task of which the computer is capable. For this reason, a stored program computer can
turn from one task to a different one whenever a new set of instructions (program) is fed into
its memory.
The first computer capable of storing instructions and data in its memory was EDSAC
It became the first stored – program computer built at Cambridge University in England in
1944. EDVAC, another stored program computer was built by Mauchly and Eckert (1946).
Mauchly and Eckert further worked on UNIVAC (Universal automatic Computer) and made
it ready for use by the census Bureau in 1951 and it was first fully electronic stored program
digital Computer to be made commercially available. It was also the first to be bought by a
business organization for data processing. UNIVAC head program was Dr Grace Hopper
who has been the first programmer of mark 1. Dr Hopper made significant contributions
toward the development of the programming language COBOL (Common Business Oriented
Language). The concept of stored program is now being used by all the present computer
system.
GENERATIONS OF COMPUTER
The series of computer from the day of invention of computer till today can be
grouped into five generations.
FIRST GENERATION COMPUTER (1940 – 1959)
The first generation of computers are valve (vacuum tubes) based machines.
Characteristics of First Generation Computers
(i)
They were large in size
(ii)
They consumed large amount of energy
(iii) They produced much heat
(iv)
They were programmed using machine language (0 and 1)
(v)
They were valve based machines
(vi)
They had limited internal memory
(vii) The were very slow in operation
(viii) Punched cards were used to enter data into the system.
(ix)
They were not reliable
Examples of the first generation computers are IBM650, ENIAC, MARK 1, UNIVAC
SECOND GENERATION COMPUTER (1959-1964)
Second generation computers used transistors as switching device instead of vacuum tubes
Transistors are smaller and they are fast and more reliable. They produced less heat during
the operation. The transistor was invented in 1948 by a team of scientists headed by williams
Shockley in United States of America. Transistors are made from material called semiconductor (silicon and germanium)
Characteristics of second generation computers
(i)
They used high level language such as COBOL, FORTRAN (FORMULA
TRANSLATOR)
(II)
The were smaller in sizes
(iii) They used transistors
(iv)
They consumed less electricity (power)
(v)
They employed magnetic core for internal storage.
(vi)
They used external storage to supplement internal storage e.g. magnetic disks
(vii) They required less air conditioning.
(x)
They were more reliable than the first generation computers.
Examples of second generation computers: Honey Well 400, Honey Well 800, IBM 401
THIRD GENERATION COMPUTERS (1964 – 1970)
The Third Generation computers began in 1964 with the IBM (International Business
Machine) 360 mainframe family. They made use of integrated circuit (IC).
Features / Characteristics of Third Generation Computers
1.
They have larger memory sizes and they are cheaper in term of cost per byte .
2.
They performed more accurately.
3.
Integration of hardware and software.
4.
Ability to perform several operations simultaneously.
5.
Data communication advances.
6.
Increased internal storage capacity.
7.
Increased speed of processing.
Examples of the third generation computers are IBM 360 series, ICL 1900
FORTH GENERATION COMPUTER 1971 – PRESENT
The 4th generation computer made use of large scale integrated circuit (LSIC) which
makes possible the design of smaller computers which are described as micro-computers. The
noticeable development of this generation includes the following:
(i)
Use of Large scale integrated circuit
(ii)
User friendly, menu drives, interactive and intelligent software system such as spread
sheets, data base management system, word processing packages, desktop publishers.
(iii) Faster memories
(iv)
Mass memories.
(v)
Highly improved building block with emphasis on standard and compatibility of both
hardware and software system. It enhances pipelining and parallel processing
FIFTH GENERATION ,COMPUTER (1990-?)
The fifth generation computer are the computer which are widely applied in business
data processing, mathematical statistical calculations in sciences and engineering. The 5th
generation computers are based on a new architect which shipment very large memory, high
parallel processing, text editing, image processing and reasoning. They can learn, associate,
make inferences, take decisions and otherwise behave in such ways that, they are considered
the exclusive province of human expert of a problem domain. They store information in a
data base which enables processing to be carried out efficiently.
The fifth generation computer is therefore intended to be intelligent as human being.
Features of The Fifth Generation Computers
(i)
knowledge of processing and inference procedural capability.
(ii)
Integration with telecommunication technology such as telephone, radio and satellite
(iii) Image processing
(iv)
Very high parallel processing and pipelining
(v)
Logic programming
(vi)
Text analysis and synthesis.
ORGANIZATION OF A COMPUTER SYSTEM
Physical Components of a Computer System
CPU (Central Processing Unit)
Control Unit
A computer system is made up of the central processing unit (CPU), visual display unit
(VDU), key board, mouse, software and other peripherals such as speakers, scanners and
printers etc.
A system is an organized way of doing things. It is the interrelationship of objects in
achieving a common goal. System could be made up of sub-system or components, which
worked together for a common goal. Computer system therefore refers to the group of
components that are working together in a regular relation to generate the required output.
The two components of the computer system are the hardware and software . live wire refers
to the people operating the computer system. Human beings cannot be a part of a machine.
HARDWARE COMPONENTS
The hardware is the machinery part of the computer system. The equipment you use, the parts
you can touch or break. The computer hardware consists of the central processing unit and
the peripheral units such as key board ,speaker, monitor (VDU) ,printer, scanner and mouse
which are used to get data into and out of the computer system.
The central processing unit.
This is the nerve centre of a digital computer and it contains three parts, they are:
(i) Main memory
(ii) Arithmetic and Logic unit (ALU) and (iii) control Unit.
Functions of CPU
(i)
It temporarily stores the programs and data currently being used so that the computer
can quickly access the information.
(ii)
In connection with the operating system, it coordinates all of the computer‟s activities,
for example retrieving files from the disk, interpreting data and commands entered
from key board (Input Unit) and sending data to the output devices such as printer.
(iii) It performs arithmetic calculations such as addition and subtraction using binary
system of mathematics.
(iv)
It performs logical operations using equal to, greater than and less than comparison.
(i) Memory Unit –
The memory unit is the section of the system where data, instruction and output are
stored or held during processing, or for onward transfer to either the control unit or the ALU
or even to an output device.
Data and programs are held in the internal storage until required. The memory of
computer can be classified into (3) three, namely: primary memory, secondary memory,
which is divided into Random Access Memory (RAM) and Read Only Memory (ROM).
RAM: RAM stores data temporarily while a program is being run it enables information to
be erased or overwritten while the user is processing data on the computer. RAM is highly
volatile, it looses information easily as a result of power failure. It enables the user to read
and also write information whenever he requires. The storage facility is very limited; it is the
main or primary or user memory.
Read only memory (ROM): It is static, non-volatile memory. It is a permanent storage
medium on chips that contain instruction and data, which are used permanently on the
computer Users can read it but the user cannot change it. Data is permanently recorded on
memory chips and turning the computer off does not affect it. ROM is generally used to store
permanent information needed by the computer for example it contains the initial programs
code, the instruction computer must follow to start up when you first turn it on. The content
of ROM can only be accessed and read by the users, It cannot be modified or erased at userlevel. Unlike RAM, it is not volatile in nature. it provides access to time to information.
Tertiary memories: Tertiary memories are located outside the processor and are not
connected directly to the processor. It supports off – line processing of data. It has a lower
access time to information than secondary memory. Examples are punch cards ,computer
(flow line) papers, magnetic tape, floppy disk and magnetic disk pack, flash drive e.t.c
(ii) Arithmetic And Logic Unit (ALU)
Calculations and comparison are done in this unit. Its arithmetic sub unit enables the
operations of addition, subtraction, multiplication and division while its logic sub unit
provides the computer ability to test various additions and take specific actions. One may be
interested in testing certain conditions.
The ALU includes Registers, Adders and counter. A register receives, holds and
transfers data as directed by the control unit. An adder receives information from two or more
sources. It performs the necessary arithmetic operations on the data and sends the results to a
register. A counter counts the number of times an operation is performed.
(iii) Control Units:- It directs the sequence of operations ,interprets the codes/ instructions
and sends signal / commands to other devices.
Functions of control unit
i.
It directs the input devices to read data into the memory.
ii.
It instructs the ALU- Arithmetic and Logic unit as to what operations to perform on
data stored in the memory and where to store the calculated results in the memory .
iii.
It instructs the output devices, what information is to be printed and on what medium
to record it.
The Pheripheral Units
The Pheripheral Units are of three types, they are:
(i) Input devices
(ii) Output devices
(iii) Auxiliary storage devices.
(i)
Input devices: These are the devices used to enter data into the computer system. e.g
key board, mouse, light pen, joystick, voice input.
(ii)
Output devices: Output devices help to bring out processed information from the
processing unit to the outside world e.g printers, VDU. Microfilm recorder, magnetic
tapes, magnetic disk and diskettes.
(iii) Auxiliary Storage or Backing Storage
Auxiliary Storage is used to provide mass storage for programs and files which are
not currently being operated on but which will be transferred to the main storage when
required. The devices include microfilm, magnetic tape unit, magnetic disk unit and floppy
disk unit.
SOFTWARE COMPONENTS
Software is the set of instructions called program that is used to instruct the computer
what to do and when to do it. The software is designed to exploit and provide the potential
capabilities of the hardware to the user. Software can be classified into two major groups:
(i)
System Software: The computer manufacturer usually provides this. It is made up of
mostly programs that contribute to the control and performance of the computer
system. Computer user cannot modify it. It controls the programs used by computer
users and hardware components.
(ii)
Application Software: They are usually produced by the users. It may also be
produced by computer manufacturer or supplier. The computer user develops his own
software to meet his personal or corporate needs. Application software are further
divide into (i) User application Program (ii) Application Packages.
CHARACTERISTICS / ADVANTAGES OF A COMPUTER SYSTEM.
(i) Accuracy
(ii) Versatility (iii) Very High speed
(iv) Storage facility (v) reliability (vi) Programmability.
CLASSIFICATION OF COMPUTERS
Computer may be classified according to
(a)
Types / Method of data representation
(b) Purpose
(c)
Size of computers.
(a)
TYPES OF COMPUTERS:
The three types of computer are
(i) Digital
(ii) Analog
(iii) Hybrid
(i)
Digital computers: These are the type of computers used to process numeric
information. Digital computer uses a very simple number system known as binary
which deals with two characters only 0 (zero) and 1 (one) to represent numbers,
letters and symbols. Digital devices include: wrist watch and light switch.
(ii)
Analogue /Analog Computers: There are some things that cannot be counted in
order to know their values. e.g. water oil, speed of a moving object, heat, height.
These are continuous objects. We can only measure these objects in volume.
Computers that handle such thing are called analogue computers. Analog computers
accept quantities varying over a length of time rather than a series of distinct items
with a unique value. They are used to measure physical quantities that are in
continuous form e.g Temperature, pressure, voltage, electric current, speed. Examples
of analog devices are electric meter, speedometer, length scale, barometer.
(iii) Hybrid Computer: These are the type of computers which combine both the
properties of digital and analogue computers. Hybrid computation involves converting
digital computer to analog computer and similarly converting analogue computer to
digital computer using a device called MODEM (Modulator and Demodulator)
(B)
CLASSIFICATION ACCORDING TO PURPOSE
There are two main classifications under purpose
(i)
Special purpose
(ii) General purpose
(i)
Special Purpose: These are the computers designed for a specific problem e.g
computer designed for accounting problem, weapon Guidance system, Electronic
wrist – watch etc.
(ii)
General Purpose Computers: These are the computers designed to solve a wide
range of problems. Special programs are written to provide solution for each of the
problems. Such computer can be used for word processing, Accounting, Statistics,
computer-Aide design etc.
(C)
CLASSIFICATION OF COMPUTER ACCORDING TO SIZE
(i)
Main Frame: They have very large size and they are early computers. They are some
how electro-mechanical devices. The users do not have direct interactions with the
computers. There are input – output clerks, computer operators, Data entry operators,
system Analysts and computer programmers which are lined up between the computer
users. Main Frame computer supports multiple programming, that is, two or more
programs or jobs can be run on a mainframe computer simultaneously.
(ii)
Minicomputers: They are physically smaller and cost far less than mainframe, yet
they are very powerful to do many of the jobs that only big mainframe computer
could do.
(iii) supercomputers: The end result of the need for large and faster computers in
scientific applications is the supercomputer. The development of supercomputers
emphasizes parallel processing and pipelining.
(iv)
Microcomputers: These are usually referred to as personal computers (PCS). They
range from the type that can be kept on a desk to models like brief cases and that
which can be kept in the palm. Microcomputers support mono programming, that is,
only a program or job can be run on them at once. Microcomputers are capable of
performing operations like the mainframe or minicomputers. They are user friendly.
Microcomputers are the smallest, least expensive of all computers.
INPUT / OUTPUT DEVICES
Input devices: These are the computer devices, which are used to enter data and information
into the computer system. Some examples of input devices are:
1.
The keyboard: This is one of the mostly used input devices. It allows data to be
keyed directly into the CPU from the key terminals. The computer keyboard
resembles the typewriter keys but different from it in many ways: some keyboards
have functions that can perform the function of a mouse.
ii.
Mouse: This is the second most commonly used input devices. The device is called
“mouse” because its shape looks so much like that of a rat,. when mouse is dragged on the
mouse pad, it moves the cursor. Mouse can move the cursor in any direction. Icons characters
are quickly located with mouse.
iv.
Light Pen: Light pen, as the name sounds and connotes is a PEN that works by light
or current or electricity. It works in conjunction with special monitor called
GRAPHICS VISUAL DISPLAY UNIT (GVDU). The GVDU has special feature of
hardware and software that is capable of detecting the light coming from the “ball
point” end of the light pen. If you had played on the sand, you must have drawn
things on it. The GVDU serves as sand while the light pen serves as your finger.
v.
Scanner: The scanner is a camera, which is capable of taking the photograph of an
object, and then pass it into the computer memory or storage for further processing.
When this is done, the computer can modify the picture in so many ways. The scanner
is connected to the system unit just as the other peripherals are. Scanner can scan a
section of a photograph by selecting the required area out of the whole. Photocopier
cannot do this.
vi.
Voice Input: Quality of voice input data can never be as the original voice due to the
conversion to binary code done by the digitizing sound sampler. The wavelength and
height determine the generated voice.
vii Card Reader: This is another Input device which works by recognizing holes in a small
card.
OUTPUT DEVICES
Output devices are the tools used to get out the result of the processed data called out
put (information)from the computer system. Output devices include: monitor (VDU), printer,
plotter, speaker and microfilm.
i.
Monitor: It displays the output or information on its screen. Such copy is called soft
copy. Its shape is very close to that of television. If a copy of what can be seen on the
screen is required on paper, it can be obtained from either a printer or a plotter or from
a turtle. Copy on paper of programs from a CPU is called hard copy.
ii.
Printer: The printer displays the output from a computer system unit on a paper. The
paper is generally called a flow line and also called hard copy. Printers can be
classified into two categories.
(i) Impact printers and
(ii) Non–Impact printers.
(a)
Impact Printers: These are the printers that print character, they use carbon papers or
ribbons to transfer impression on the paper or flow line. Each head is hit by a
hammerhead against a carbon paper to make the character visible. e.g line printers,
daisy wheel printers and dot matrix printers.
(b)
Non-Impact Printers: These have no character head (s) do not use carbon paper but
rather TONER (liquid ink) through electronic beams e.g ink jet printers, thermal
printers, laser printer.
iii..
Plotters: The plotters are the right devices for drawing pictures and graphs. Plotters
are usually called graph plotters. Plotters use pen that can move in different
directions. However there are plotters that use electrostatic printing rather than pen
and ink. Colour graph plotters use many pens, each for a colour instead of one pen.
iv.
Speaker: The output device that provides sound information is the speaker. The
system unit output, which is in digital form, passes through a “digitizing sound
sampler” which produces a waveform. The waveform is connected to a vibrator,
which produces sound .The sound we hear is nothing but vibration received by the
eardrum.
v.
Computer output on microfilm (COM): Modern, high resolution photographic film
is capable of storing large quantities of data in readable character form in a relatively
small space, and is consequently useful as an output medium for data that is required
to be stored (archived) or sent by post. Photographic output takes two forms;
microfilm and microfiche.