2. Introduction
After having an overview of computer
systems, let us now move on to learn
how they have evolved over the
years, from a computer that filled a
whole room to one which can fit in
your hand.

3. The History of Computers
The first electronic computers were
produced around 1940s. This was after a
gradual change from the traditional
processing aids E.g. abacus, slide rule
etc. Some of the saline historical events
as concerns the research towards
computers origination are described
below.

4. AN ABACUS

5. In 1614, logarithm as an aid of
calculation was invented by a Scottish
mathematician known as John Napier,
who subsequently invented a rod of
bones, the idea which was in use
three years later after his logarithm
invention and was employed in
carrying out multiplications.

6. Napier’s Bones

7. In the year 1620, the slide rule was
invented by William Oughtred an English
man.
In 1623, the idea of using binary numbers
to represent e.g. characters, what was
described as the binary codes was
invented by Francis Bacon.
In 1642, the calculating machine, which
had both the ability to add and to subtract
numbers, was invented by Blaise Pascal.

8. Pascal’s calculating machine

9. In 1671, a calculating machine which had
got the capability to multiply and to divide
numbers was invented by Gottfried Von
Leibniz.
At around 1802, a Jacquard Loom was
invented by Jacquard. The machine was
used to store instructions for weaving on
the punched cards. This formed the basis
for the programmable computer.

10. Jacquard Loom

11. In 1822 Charles Babbage, a professor of
mathematics invented the model for the
difference machine, whose design he did not
complete but he later in 1834 used the same
idea to develop a general purpose calculator,
whose design was very close to the design of
the computer today. . He is usually referred to
as the grandfather of computer science. He
built a computer theoretically, but his ideas
were too advanced for the available
technology.

12. Charles Babbage
The grandfather of computers

13. Between1847–54, George Boole
discovered Boolean algebra, whose
principles are the basis of today’s
computer logic gates used as logical
elements.
Around Mid 1880s the tabulator machine
was discovered by the Herman Hollerith,
the machine had the capabilities of
detecting data stored in terms of punched
holes on the cards. Hollerith’s company
later became IBM of today.

14. Data stored in punched cards or tape
must be read and interpreted into an
understandable language. His ideas
contributed to the invention of
punched card readers and paper tape
readers used in the first generation of
computer systems.

15. Hollerith’s Machine

16. In 1900, the magnetic storage media
principles as on e.g. magnetic tapes was
discovered by Valdemar Poulson.
Magnetized storage is used a lot in
computer systems.
 At around 1906, thermionic valves was
invented by the Lee de Forest. The
valves were useful in the electronic logics
implementation. This were used for
internal storage of first generation
computers.

17. In 1937, Automatic Sequence Controlled
Calculator (ASCC) was developed by
Howard Aiken and IBM. In 1959, Aiken
developed punched paper tape, to be
used as an input medium.
In 1938, Claude Shannon established
how Boolean algebra could be applied in
the design of the computer’s logical
circuits. This concept is still used in
present day computers.

18. In 1941, the calculating machines, Z3 and
Z4 were developed by Konrad Zuse and
these machines had the ability to use
programs. Lady Ada is claimed to
possibly be the first programmer. Ada a
programming language was named after
her in honor of her contribution to
computer programming concept.

19. Aiken worked out a plan, to set
mechanical calculators to work on
mathematical problems in control
sequences. He set up a project to develop
the necessary equipment and with the
support of International Business
Machines Corporation and Harvard
University, and assistance from four co-
workers from IBM, he built the first
computer.

20. This machine, called International
Business Machines Automatic
Sequence, Controlled Calculator, and
also known as the Harvard Mark 1
computer was presented to Harvard
University in August 1944. It was the
first information processing machine
and it was electrically powered.

21. Aiken’s Machine

22. In 1946, Electronic Numerical
Integrator and Calculator (ENIAC)
was in use, developed by Presper
Eckert and John Mauchly. The
machine used valves and consumed
a lot of power. It was water cooled. It
was huge, taking up the walls of a
room, 20 x 40 feet in size. This was
the first electronic computer.

23. Figure ENIAC

24. In 1946, Von Neumann gave a report
on the design which forms the basis of
today's computer. He demonstrated
that one could encode instruction to
the machine, in the same language
used for the data it processed. This
brilliant demonstration made it possible
to mix instructions and data in the
program as both could also be stored
in the computer.

25. John Von Neumann’s Machine

26. All of the above had contribution to
the present day computer which is
being improved on as the time goes
by. Their ideas are still being
researched and used in computer
systems.

27. Computer Generations
Following the development of the first
electronic computer in 1946, the historical
events in respect of computer
development are not considered
individually or in terms of individual years
but in classifications of durations of
periods known as “generations”. A
generation groups computers of like
technological characteristics.

28. The transition from one generation to
another was, and is influenced by the
amount of research towards further
development of the computers, and
the related facilities and concepts.
We shall now describe computer
generations:

29. First generation Computers
These were the earliest time
computers, which were in use from
around the mid 1950’s to late 1950,s.
They used big physical devices in
their circuitry and hence were very big
in their physical size. Their circuits
incorporated the thermionic valves,
a non solid state electronic device as
a major logic element.

30. These computers
Consumed a lot of power generating a lot
of heat and hence non-reliable as the
circuitry components were prone to failure.
They had limited internal memory which
was based on the use of delay lines
The processor worked at slow speed as
compared to the speeds of the computers
of today.

31. Their design was based on the
John Von Neumann’s
recommendations.
Examples of the first generation
computers are UNIVAC and a
commercial computer known as
Lyon’s Electronic Office (LEO).

32. Second Generation Computers
These were computers of the
closing of the 1950s to the
early1960s which used transistors.
The transistors are relatively smaller
than valves and consume
comparatively less power and
therefore, the resulting computers
were more reliable and
comparatively small in size.

33. The transistors were based on the solid-
state technology, where the electric
pulses were not to flow through a vacuum
as in the case of the thermionic valves of
the first generation computers.
The second-generation computers’
internal storage was higher than those of
the first generation computers. The core
memory replaced the delay lines and the
magnetic drums, the internal memory of
the first generation computers.

34. The second-generation processors
operated at a comparatively higher
speed than those of the first
generation computers.
The design of these second
generation computers/processor was
on a family basis; that is one family of
computers had a set of related
technological characteristics.

35. These computers had programming
languages whose vocabularies are
close to the human language,
specifically the English language.
Examples of the second-generation
computers include IBM 300 Series
and ATLAS.

36. Third Generation Computers
The computers of this generation came
into being towards the mid 60’s and they
used integrated circuits to replace the
second-generation computer physical
transistors.
The integrated circuits combine several
physical electronic components within a
small crystal called the silicon chip (IC-
Integrated Circuit).

37. The resulting computer was reduced
in sizes as compared to the second-
generation computers.
The small circuitry that resulted,
improved the processing speed for
pulses as data pulses could flow
faster from one module to another as
compared to the flow within the larger
circuits, where they travel
considerable distances.

38. The third generation computers had
higher main memory capacity..
These computers were of increased
processing power as compared to the
second-generation computers, and
therefore, had the capability of holding
more than one set of instructions
(programs) – Multiprogramming.
Could support more than one user

39. These computers had the capability
to support communication facilities i.e.
remote communication facilities.
Users could be in remote locations or
the same location
 Examples of such computers are
ICL 1900 Series, IBM 360.

40. Fourth Generation Computers
The fourth generation computers
resulted from a modification of the
third generation computer’s
technology. The design of this
computer is based on Large Scale
Integration (LSI) of circuitry and
Very Large Scale Integration (VLSI)
of circuitry.

41. This generation marked the origin of
mini computers in use today.
The design of the fifth generation
computers was based on the VLSI
technology that gave rise to PCs.
The microcomputers are usually
described as PCs or stand-alone or
desk top computers because they
were primarily to serve a single
person at a time.

42. Fifth Generation Computers
The fifth generation is still a
state of the art of technology
that relies on predictions and
further technological
refinements.

43. Trends in Computer Technology
The trend in the computer’s technological
revolution can be summarized as follows:
Continual decrease in computer size
Improved speed and power of
processing
Decrease in computer’s and its related
facilities cost
Increase in the number of components
per circuit (IC).

44. Computer Classifications
Because of the variations in
characteristics of computers, computers
can be categorized by:
(a) Data Manipulated
Analog computers
Digital computers
Hybrid computers

45. (b) The purpose for which they are
designed :-
 General purpose computers
 Special purpose computers
 Dedicated Computers
(c) The basis of price, size and
capabilities
 Main frame computers
 Mini computers
 Micro computers
 Personal computers

46. Classification of Computers by the
Types of Data Manipulated
Analog computers perform
arithmetic operations and logical
comparisons by measuring changes
in physical magnitudes such as,
electronic voltage, pressure changes,
and temperature changes.

47. The application of analog computers
is confined to specialized areas as in
scientific or engineering experiments,
manufacturing processes and military
weapons.
The examples of analogue devices
include thermometer and car
speedometer.

48. The output from the system may be
in the form of a graph produced by a
plotting pen or a trace on a cathode
ray tube. Its output signals can be
used directly to control the operation
of some other machine or process.

49. Digital computers are the most
commonly used type of computers.
Their arithmetic operations and logical
comparisons are based on digits (1s
and 0s) and on other characters that
have been numerically coded.
These computers can process both
numeric and alphabetic or
alphanumeric data. Memory sizes
determines capability

50. These types of computers are used
in a wider cross section of the
application areas such as scientific,
industrial and most of the other
computer based data processing
applications. The digital computer
also has a unique ability, and that is,
storing large quantities of data.

51. Hybrid computers are designed by
interconnecting the digital computer
and analog computers’ element
directly into one processor, using a
suitable interfacing circuitry. That is,
both the digital and analog features
are built within the same
computer/processor.

52. Because of their capabilities they are
more expensive. For example in a
hospital ICU unit, analogue devices
may measure a patient’s heart
function, temperature and other vital
signs. These measurements may then
be converted into numbers and
supplied to a digital device which may
send an immediate signal if any
abnormal readings are detected.

53. Special Purpose Computers are
digital computers are designed to
carry out special processing tasks in
one or more applications.
For example, in a computer network,
a special type computer known as the
Front End Processor (FEP) may be
used to specialize in the work of
network control,

54. General Purpose Computers are
digital computers designed to be used
in a variety of application
environments as required. This
capability of the computers is made
possible by passing into the computer
the relevant sets of instructions, to be
used by the computer to carry out the
desired different processing tasks at
any given time.

55. Dedicated Computers are general-
purpose computers that are
committed to some processing tasks.
They are nevertheless capable of a
variety of tasks. A general-purpose
computer, for example, can be
dedicated to carry out airline
reservation.

56. Classification of Computers Based
On Price, Size and Capabilities
In terms of capacity, price and
performance criteria, computers can
be further categorized as follows:
Mainframe computers
Minicomputers
Microcomputers
Personal computers

57. Mainframe computers are most
expensive of all the computers and
are very big in size and offer the
maximum computing power. A large
number of peripherals can be
attached to them. They are generally
used in large networks of computers
with the mainframe being the nodal
point of the network. Smaller
computers are included in the

58. A typical application of mainframes is
found in the airline reservation
systems. The airlines have a
mainframe computer at their head
office where information of all the
flights is stored. Smaller computers,
installed at the booking offices, are
attached to the central data bank so
that up-to-date information of all
flights is always available.

59. They can accept and transfer data from
input/output devices at the rate of millions
of bytes per second.
These are big general purpose computers
capable of handling all kinds of problems
whether scientific or commercial.
They can accept all types of computer
languages.
They can support a large number of
terminals.

60. They usually have instruction sets
that give them the flexibility to operate
automatically.
They have large on-line secondary
capacities and can support a number
and variety of peripheral devices
They routinely have high speed
cache memory, which enables them
to process applications faster than
mini or micro computers

61. Example of a mainframe computer

62. The minicomputers are medium
sized computers. They support
average internal and backing
storage. Their storage capabilities
both internal and external are
comparatively higher than the
microcomputers but lower than the
mainframe.

63. They are more powerful and
reliable than the microcomputers
though slower than the
mainframes. They are more costly
than the micros but cheaper than
the mainframes.
Minicomputers are used mainly
in medium scale businesses

64. Mini Computer

65. Microcomputers are computers of
advanced technology that became
available in the late 1970’s. The
advent of micro computers brought
computers within reach of even the
small businesses. The
microcomputers are the most
common form of computers in offices
today. They include the desktop,
personal or standalone systems.

66. The micro computers are the
smallest of the three computer
classes. Their design is based on
large scale circuit integration that
confines several physical
components to smaller elements,
the size of a thumb.
Their internal memory is smaller
than the mini computers and the
mainframe computers.

67. The micro computer configuration
typically includes: A monitor, a
keyboard, Winchester disk (hard
disk), a mouse, a printer, a diskette
drive and an optical disk drive. Can be
connected to larger computer.
Note: this configuration is changing
and, therefore making the micro
computer very powerful. Some of
them are able to support more than
one user.

68. Micro Computer

69. Generations of Programming
Languages
We have seen how computers have
developed over the years, but one
thing we have to keep in mind is that,
computers are “dumb” machines.
They can only do what they are
instructed to do. Instructions that are
given to the computer are called
programs and they are given in
different languages.

70. Machine Languages (First
Generation Language)
Machine language is a programming
language in which the instructions are
in binary code, or machine code.
Each instruction corresponds directly
to a hardware facility on the machine
for which it is written. No further
interpretation is necessary

71. This language is machine dependent,
meaning that each computer has its
own machine language.
This is the most basic level of
programming language. In early
stages of computer development, all
instructions had to be written using
this language.

72. Assembly Languages (Second
Generation Languages)
Assembly languages are low-level
languages. They were developed to
reduce the difficulties in writing
machine language. They are
machine oriented meaning that they
are close to machine vocabulary
rather than human vocabulary.

73. Each instruction resembles a
machine instruction; mnemonic codes
are used instead of machine code.
Assembly languages must be
translated to machine language
before use by the computer. A
manufacturer usually avails the
language.
Features of these languages differ
from computer to computer.

74. High-Level languages (Third
Generation Languages)
The development of low level
languages was a great achievement,
but was still dependent on the
machine, meaning that it could not be
imported to different machines. Thus,
there was a need for high level for
high level languages.

75. High-level languages are machine
independent and are problem-
oriented languages. They reflect the
type of problem to be solved rather
than the features of the machine.
Machine independence means that in
principle it should be possible to make
the same high-level languages run on
different machines. Programs should
also be portable. In this instance:

76. Users can change computer without
the need to rewritten programs.
Users of different computers may be
able to share or exchange programs
and reduces costs.
An organization producing software
for sale can sell the same program to
users of different computers without
the need to rewrite the programs for
each type of computer.

77. Very High-level Languages (Fourth
Generation Languages)
4GLs are user oriented rather than
problem oriented. They are easy to
learn and understand because they
are user based. The languages
syntax (grammar) is natural, near
English. It uses menus and prompts
to guide a non-specialist to retrieve
data at ease.

78.  Very little training is essential before
these language’s programs can be
used or developed. They continue to
grow. An example is Microsoft
access.
Fifth Generation Languages
These languages are still in a state of
development. They are not famous in
the market and to programmers.

79. Translators
A translator is a program that
converts statements written in one
language, to another language. There
are three types of translators:-
Assembler. A language that
translates assembly language into
machine code.

80. Compiler. A program that translates
high level language into machine
code
Interpreter. A program that
translates an instruction into an object
code and works on it immediately.

81. RECAP
Who is the father/grandfather of computers?
Francis Bacon discovered binary numbers, why is this
invention useful in today’s electronic devices?
There are two first computers, Aikens MARK I and
ENIAC by Eckert an Mauchly, what is the difference
between the two computers?
Why are fouth generation computers smaller and
faster than the earlier computers?
Describe a hybrid computer.
What is a machine language?
Classify computers by their price, size and capability

82. END