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‘’’qUnit 1 Introduction to Computer
Expected Duration: 2hrs
Introduction
In this lecture you will learn about information and Communication Technology (ICT), as you know, we
are now in information age and every aspect of our life depends on information technology. Therefore in
this course you will learn about definition of computer, its historical development. You will also learn
about great computer scientist who contributed to development of computer.
its applications in different areas of human endeavour such as banking, education, science, health,
agriculture etc. The course will also take you through memory lane of computer developmental stages and
characteristics.
Learning Outcome for Unit 1
At the end of this unit, you should be able to:
1.1 Define computer
1.2 Explain historical development of computer
1.3 Explain the contributions of the great computer scientist to developments of computer.
1.1 The Meaning and Characteristics of Computer
1.1.1 Definition of Computer
There is no doubt that man is highly gifted and is of high capabilities and potentials. In fact, man
is truly an amazing being and a master of inventions. He constantly uses the power of his
imaginations and inventions to solve problem in his environment. A lot technologies have been
developed, be it television, vehicle, camera, radio etc. are his inventions. Computer is not an
exemption, it is one of the inventions of this amazing being. Therefore, what is a computer? A
computer is an electronic machine used in solving problem. This definition of computer that you
just read is just a simple definition, it does not say enough about computer. This is because not all
electronic machines are computer. You should also note that computer is not just physical
equipment that you can only see or touch, it is also made up of parts you cannot easily see like the
program. Now in a more encompassing manner, let us define computer. Computer therefore, is an
electronic device (calculating machine) that is capable of accepting data (Input), process the data
logically or arithmetically using some sets of instructions (Processing) and release result
(Output).
In another way a computer can be defined as an electronic machine that solves problem by
applying prescribed instructions on data represented to it. To the present day generation,
computer has different meaning to different group of people. The use to which it is put
determines the understanding attached to it. It is common for different group to see it differently
because of differences in usage. As you study along, bear it in mind that computer is not
composed just a machine, but it is a collection of interrelated parts which are able to transmit
information to one another
Fig 1.1: to be inserted
1.2 Historical Background of Computer
1.2.1 ABACUS
Historically, computing may be considered to have begun with ABACUS, which originated about 5,
years ago. During the Middle age, the abacus was used throughout the European and Arab Worlds as well
as in Asia. The design is simply a wooden rack holding parallel wires on which beads are strung.
Calculations can be performed manually by sliding (beads or blocks) along the parallel wires (rods). The
counters are divided into two sections by means of a bar perpendicular to the rods. One section has two
counters, representing 0 and 5 depending upon their position along the rod. The second section has four or
five counters, representing units. Each bar represents a significant digit, with the least significant digit on
the right. Another computing instrument, the ASTROLABE, was also in use about 2,000 years ago for
navigation.
computations. Most of the basic elements of the modern digital computer was found in Babbage’s engine
which includes punched –card input/output medium, arithmetic unit, memory for storage of numbers and
sequential control. Charles Babbage invention marked the beginning of modern computer architectural
design. Considering this great achievement he was referred to father of modern computer. Although he
was not able to implement his design because of level of technology as at his time.
1.2.5 GEORGE BOOLE
The essays written during the mid-
th
century by Boole was of greater significance. He called attention
to the analogy between the symbols of algebra and those of logic as used to represent logical forms.
Boole’ system with its binary logical operators (e.g. AND, OR and NOT) became the basis of what is
now known as Boolean algebra on which electronic computer switching theory and procedures are based.
1.2.6 HERMAN HOLLERITH
Introduction of punched cards in 1880 by Herman Hollerith a U. S. Statistician who worked on census
return was another major step in computer development. He recognised the possibility that a pattern of
holes in perforated sort and manipulate electrically by a machine specially designed to sort and
manipulated the numerical data represented by the holes. By the U. S. Census of 1890, Hollerith had
invented a tabulating system that automated census count. As stated earlier Hollerith’s system had
accomplished in one year and seven months what it would have taken a hundred clerks seven years and
eleven months to do. Hollerith left the census bureau in 1896 to form the tabulating Machine Company
which was eventually changed to the International Business Machine Corporation (IBM), which today
stands out as one of the largest computer manufacturer in the world.
Fig 1.3: punch card
1.2.7 AUTOMATIC CALCULATOR
In 1939 John V. Atanasoff, a U. S. Mathematician and Physicist built what some consider to be a
prototype of an electromechanical digital computer. That same year Howard Aiken of Harvard
University, in association with engineers of International Business Machine Corporation began work on a
fully automatic large-scale calculator using standard business machine components. By 1944 the first
calculator called Automatic Sequence Controlled Calculator, commonly known as Mark-1 was made.
Later Mark-2 and Mark-3 were built on similar line.
Fig 1.4: Automatic calculator
Another machine called ENIAC (Electronic Numerical Integrator and calculator) which consists of
switches and interconnecting wires was built around 1939, this was mainly for calculating trajectories and
could also be used in other computations. The use of paper tape for data entry into these machines was
slow and did not allow the machine to operate at full speed. Similarly there was a need to make programs
available internally along with the data, to take advantage of the high speed inherent in electronic
systems. Large memory was designed in Cambridge by M. V. Wilkes. His machine called EDSAC
(Elect`ronic Delay Storage Automatic Calculator) was used for the training of a whole generation of
computers oriented mathematicians at Cambridge. Between 1945 and 1950, EDVAC (Electronic Discrete
Variable Computer) was designed. This machine emphasized the idea of stored program. By 1948 a
prototype machines at Manchester was completed. Later, companies like IBM, Remington Co-operation
ICL and many other joined in producing computer in commercial quantities.
It stores vast quantities of information and also retrieves any given volume within a very short time gap.
One major advantage is the ability to take some decisions by altering the flow instructions.
Due to speed and accuracy of processing, computer machine are fast more becoming more popular and
there is increase in their demand n the world over. It is currently having a proud influence on science,
business, government, industry, and education.Science and mathematical research have been vastly
accelerated by the use of the computer. In business and government, management practices have been
revolutionized by computer and also because of its ability to process data and present it in a more
meaningful form. The development in the computer industry is so fast that latest developments today may
be out dated within 2 years. This continuous revolution and development in the computer industry makes
it challenging area to be exploded.
Today’s computers come in a variety of shapes, sizes and costs. Larger general-purpose computers are
used by many large corporations, universities, hospitals and government agencies to carry out
sophisticated scientific and business calculations. These computers are generally referred to as
mainframes. They are very expensive (some cost millions of dollars), and they require a carefully
controlled environment (temperature, humidity, etc.). As a rule, they are not physically accessible to the
scientists, engineers and corporate accountants that use them. Mainframes have been available since the
early 1950s, but very few people had any opportunity to use them, particularly in the earlier years. Thus it
is not surprising that computers were viewed mysteriously and with some suspicion by the general public.
The late 1960 and early 1970s saw the development of smaller, less expensive minicomputers. Many of
these machines offer the performance of earlier mainframes at a fraction of the cost. Many business and
educational institution that could not afford mainframe acquired minicomputers as they became
increasingly available. By the md-1970s, advances in integrated circuit technology (silicon “chips”)
resulted in the development of still smaller and less expensive computers called microcomputers. These
machines are built entirely of integrated circuits and are therefore not much larger (or more expensive)
than a conventional office typewriter. Yet they can be use for a wide variety of personal, educational,
commercial and technical applications. Their use tends to complement rather than replace the use of
mainframes. In fact, many large organizations utilize microcomputers as terminal or workstations that are
connected to a mainframe computer (or series of mainframes) through a communication network.
Particular interest is the development of the personal computer a small, inexpensive microcomputer that is
intended to be used by only one person at a time. Many of these machines approach small minicomputer
in power. Moreover, their performance continues to improve dramatically as their cost continues to drop.
Personal computers are now used in many schools and small business, and it appears likely that they will
soon become a common household items.
Summary of Unit 1
In Unit 1, you have learned that:
- A computer is an electronic device (calculating machine) that is capable of accepting data (Input),
process the data logically or arithmetically using some sets of instructions (Processing) and release
result (Output).
- Computer was developed through effort and contributions of great computer scientists.
Self-Assessment Questions (SAQs) for Unit 1
Now that you have completed this study session, you can assess how well you have achieved its Learning
Outcomes by answering these questions. You can check your answers with the Notes on the Self-
Assessment Questions at the end of this Module.
SAQ 1.1 (tests learning outcome 1.1)
How can we correctly define computer?
SAQ 1.2 (tests learning outcome 1.2)
Briefly discuss contribution of Charles Babbage and Blaise Pascal.
Name the people who designed the following machines
(i) Difference engine
(ii) Pascaline
Notes on the Self-Assessment Questions (SAQs) for Unit 1
SAQ 1.1: A computer is an electronic device (calculating machine) that is capable of accepting
data (Input), process the data logically or arithmetically using some sets of instructions
(Processing) and release result (Output).
SAQ 1.2: Charles Babbage proposed the architecture of the modern computer while Blaise Pascal
developed a adding machine also known as pascaline.
Difference engine - Charles Babbage
Pascaline - Blaise Pascal
SAQ 1.4: Fist Generation - Vacuum tube.
2.1.2 FIRST GENERATION
J. P. Eckert and John W. Mauchly ushered in the first generation of modern-day computers with ENIAC
(Electronic Numerical Integrator and Calculator) in 1946. It was the first all-purpose, all electronic digital
computer. Unlike earlier machines, it used vacuum tube instead of relays as its active logic element.
There was substantial increase in computational speed due to the use of electron tubes. This computer was
more than 1000 times faster than its electromechanical predecessors and could execute an average of
5,000 basic arithmetic operations per second.
In 1974 the Hungarian mathematician John Von Neumann devised a method of converting the ENIAC
concept of an externally programmed machine to that of a stored program concept. This stored-program
concept led to development of the self – modifying computer. Other notable first generation electronic
digital computers included the UNIVAC-1 (Universal Automatic Computer) built in 1951. This also
utilized vacuum tubes, its main memory consisted of mercury relay lines.
This memory system permitted an access time of about 500 micro seconds. UNIVAC-I was first
computer to handle both numerical and alphabetical information with equal ease and assailed the principle
of the separation of input/output from computation per se.
The main problem encountered during the era of the first generation computers was that they occupied
large amount of space and large circuits were involved. Generally, they were slow in operation and
generated a lot of heat with the problem of unreliability compared to other generations. The period of this
generation spanned mid – forties to mid – fifties
Fig 1.7: First generation Computer
2.1.3 SECOND GENERATION
This generation was between late fifties and early sixties. Invention of semi-conductor device known as
TRANSISTORS in electronic engineering led to the development of this generation of computers. After a
series of development in transistors for about 10 years, it became a viable alternative to the vacuum tube.
The small size of the transistor, its greater reliability and its comparatively low power consumption made
it tar superior to the latter.
By using transistors in control, arithmetic and logic circuits along with an improved magnetic core
memory manufacturers were able to produce more efficient, smaller and faster (50,000.00) operations per
second) digital systems.
The transistors helped in building a series of processors operating at microsecond speed ranges with lower
level of generated heat.
Fig 1.7: Second generation computer
2.1.4 THIRD GENERATION
During late 1960’s and 1970’s an important technological innovation resulting in dramatic advances in
computers hardware the breakthrough in the fabrication of the integrated circuit(IC), a solid-state device
consisting of hundreds of transistors, diodes and resistors on a tiny silicon chip. The impact of integrated
circuitry permitted the construction of mainframe (large-scale) computers of higher operating speed,
capacity reliability at substantially lower cost. It also helped the engineers to design mini computers.
The next major development was Large Scale Integration (LSI) which made it possible to pack thousands
of transistors and related devices on a single integrated circuit. This also led to the invention of the micro
- processor which is an integrated circuit on a single silicon chip that contains all the arithmetic, logic and
control circuitry which make up a digital computer CPU. The CPU (Central Processing Unit) is the part
of the digital computer that interprets and executed instruction. The development of the CPU into a single
integrated circuit led to the production of microcomputers.
experience. It is also expected that they would not have to be instructed step by step as to how to carry out
specific task as required by current computers. There is hope that simultaneous execution of several
separate operations (e.g. memory, logic and control) by means of numerous integrated circuits in which
millions of CPU, memory, and input/output circuits are combined on a single chip.
Fig 1.9: fifth generation of computer
Manufacturers are expected to produced voice-input device capable of handling connected speech of
larger vocabularies. A summary of the development and the generation of computers from its early days
to the present day showed in the chart fig 1.1.
A summary of the development and the generation of computers from its early days to the present day is
shown in the chart of Fig 1.
General
timing
Mid-forties
to
mid – fifties
Late fifties to
early sixties
Late sixties to
seventies
In the
eighties
In the future as
it is not yet in
market
Archite
cture
It uses vacuum tubes
as its active logic
elements
It uses transistors,
control,
arithmetic and
logic circuits
It uses fabricated
Integrated Circuit
(IC)
It uses
very Large
Scale
Integration
(VLSI)
It is expected
to be different
from Von
Neumann’s
model
Unique
feature
develop
ment
Universal Automatic
Computer
(UNIVAC-1)
It is an alternative
to vacuum tube,
low power
consumption and
reliable
LSI/CPU Artificial
intelligence
(AI)
Operati
on per
speed
5,000 basic
Operation per
second
operation per
second
Higher
operation/second.
Higher
operation
per second
Higher
operation per
second is
expected
Speed
Access
time
Its access time as
500 micro second
It has a micro
second speed
range
Higher speed Higher
speed
Higher speed
is expected
Heat
generat
ed and
power
consum
ption
A lot of heat & high
power consumption
Low range of heat
consumption
power
Low range of heat
and low power
consumption
Low heat
generation
& low
power
consumpti
on
Low heat
generation an
low power
consumption
Memor
y Space
circuit
Space
Large amount of
space and large
amount of circuit is
involve
It use small size
transistor
It contains
hundreds of
component on
tiny silicon chips
0.2inch
square
silicon
amp
contain
thousands
of
componen
ts
Expected to be
very small
Cost Higher Cost High cost Low cost Relatively
low cost
Relatively low
Summary of Unit 2
In Unit 2, you have learned that:
- Computer has generations and that each generation is a reflection of its developmental stages
- Each generation of computer has distinctive features: size, heat generation, memory size,
processing speed and the technology used in building the computer of that generation..
Self-Assessment Questions (SAQs) for Unit
Now that you have completed this study session, you can assess how well you have achieved its Learning
Outcomes by answering these questions. You can check your answers with the Notes on the Self-
Assessment Questions at the end of this Module.
SAQ 2.1 (tests learning outcome 2.1)
List five(5) generation of computer you know
SAQ 2.2 (tests learning outcome 2.2)
Explain feature of the fifth generation computer
SAQ 2.3 (tests learning outcome 2.3)
State the unique characteristics of each computer generation?.
achieve a goal. Most systems have input, process and output stages as illustrated with the diagram
below.
ii
fig3.3: Input-Process-Output system
Input: this is the element that enter the system for processing
Processing: This organises or arranges input into an output
Output: This is the result obtained from processing activities
To facilitate understanding of input-process-output processing in a system we shall use digestive
system, and human body as an illustration
3.1.1 Digestion of food as a System
Digestion of food is the taking in of food through the mouth, breaking down the foods into
soluble forms and wastes by body enzymes and releasing the wastes in form of urine and excreta.
The I-P-O phase in the system involves the following:
Input: foods
Process: breaking down the foods
Output: waste inform of urine and excreter
3.1.2 Human body as a system
You can take a look at the figure 3.4 below. It shows different parts of human body. The parts can
be likened to I-P-O system. That is, it has input, processing and output components
Fig3 .5: Human body system
Input:
- Eyes: for sensing object
- -Ears: for hearing sound
- Mouth : for drinking and eating
- Nose : for breathing in oxygen
Processing
- Brain : for thinking, memorising and controlling the activities of the body
INPUT
PROCESS
OUTPUT
Output
- Hands: for writing information
- Mouth for speech
- Nose for breathing out carbondioxide
3.1.3 Computer as a system
The definition of computer you read in unit 1 of this module shows that computer is an I-P-O
system. From the definition, computer accepts data (input), processes the data and gives out
results(output). The I-P-O is represented in figure 3.6 below
INPUT PROCESS OUTPUT
Figure 3.6: Input-Process-Output-Phase in Computer
Consider this scenario: suppose numbers 10 and 15 are supplied to a computer with an instruction to add
the two numbers. Can you show the I-P-O phase of how computer will carry out this scenario.
The computer will add the two numbers according to the given instruction and generate the required result
which is 25. The I-P-O phase of the addition operation of the two numbers is represented in figure 3.
below
INPUT PROCESS OUTPUT
Figure 3.7: I-P-O PHASE
3.2 Computer System
In our earlier study in unit 1 we gave simple definition of computer. You have also further studied that a
computer is a system. What then is a computer system? A computer system is not a single machine. It
consists of a group of electronic components like monitor, system unit, keyboard, mouse, printer and
other components working together to achieve a particular goal. You can see figure 1.1 for different
components of a computer systems
3.2.1 Characteristics of a Computer System
Computer has some characteristics or features which distinguish them from other machine. These
characteristics constitute the advantages of computer. Below are some of these characteristics
Execution Data
Results
Add
10 to 15
10 and
A large computer may have several millions words of memory. Some memories have ability to
store 16,000 or 64,000 bits (pieces of information) and there are others that can store information in the
region of gigabytes (1 gigabyte 1024 * 1024 = 1048576).
Now can you calculate the capacity of this computer in term of data storage?
o If the memory of a large general purpose computer is 2048kb, can you determine the storage
capacity of the computer?
Then this is equivalent to 2048 * 1024 = 2,097,152 words. If the entire memory is used to
represent numerical data, then roughly 2 million numbers can be stored within the computer at
any one time. If the memory is used to represent character rather than numerical data, then
about 8 million characters can be stored at any one time. This is more than enough memory to
store the content of an entire book.
Most computers also employ auxiliary memory device (e.g. magnetic tapes, disks, solid-state memory
devices) in addition to their primary memories. These devices typically range from a few hundred
thousand bytes (for a small computer) to several million words (for a larger computer). Moreover, they
allow for the permanent recording of information, since they can be physically mounted or dismounted
from the computer and stored when not in use. However the access time (i.e. the time required to store or
retrieve information) is considerably greater for these auxiliary devices than for primary memory.
SPEED AND RELIABILITY: Because of its extremely high speed, a computer can carry out
calculations in just a few minutes that would require month’s perhaps even years – if carried out by hand.
Simple tasks, such as adding two numbers, can be carried out in fractions of a microsecond (1 us = 10-
6s). On a more practical level; the end-of-semester grades for all students n a large University can
typically be processed in just a few minutes of computer time. For example it was estimated that
Hollerith’s system had accomplished in one year and seven months what it would have taken hundred
clerks seven years and eleven months to do.
This very speed is accompanied by an equally high level reliability. Thus a computer practically never
makes a mistake of its own accord. Highly publicized “computer” errors such as a person receiving a
monthly bill of a programming error or an error in data transmission rather than an error caused by the
computer itself. In computer systems, output could be described as 100% reliable if the input is correct.
Hence the saying garbage-in, garbage-out (what you send n, is what you must expect).
Activity 1.
Take a moment to reflect on what you have read so far. Based on your learning experience, and knowing
that computer has a lot characteristics which make them to be very useful for daily activities. Can you
mention some of the advantages, individual, organisations and even government can derive from using
computer?
Activity 1.1 Feedback:
The advantages of computer ranges from speed, accuracy, storage capacity, integrity and security. Read
more from unit 3.2.
3.3. Types and Classifications of Computer
3.3.1 TYPES OF COMPUTERS
There are two basic types of computers namely
(1) Analogue Computers and
(2) Digital Computers.
The analogue computers operate on data represented by variable physical quantities , such as voltages
and are measured continuously.
Digital computer on the other hand works with numbers, words and symbols expressed as digits, which
it manipulates and counts discretely.
ANALOGUE COMPUTERS
An analogue device is defined as one that operates on the principle of similarity in proportional relations
to a process modelled when values are kept constant over a specified range. A computer of this type
solves problems by operating on continuous variables rather than on discontinuous or discrete units as
do digital computers. Analogue computers are similar to a voltmeter in the way they measure values.
They translate various physical conditions such as flow, temperature, pressure, mechanical motion, and
angular position into mechanical or electrical analogue values.
These types of computer uses various types of amplifiers to perform arithmetic operations as
summation and multiplication.
