Computers
A microcomputer is a small, relatively inexpensive computer with a microprocessor as
its central processing unit (CPU). It includes a microprocessor, memory and minimal
input/output (I/O) circuitry mounted on a single printed circuit board (PCB). Microcomputers
became popular in the 1970s and 1980s with the advent of increasingly powerful
microprocessors. Start here.
Outcome of Learning
Upon a successful completion of the unit’s content, you should be able to:
1.1. Describe the generation of computers
1.2. Identify the types of computers
1.3. Identify the main components of a computer
1.4. Define and identify categories of computer software
1.5. Illustrate the computers Information processing
1.6. Understand data communications and Computer Network
1.1 Generation of computers
What is a computer?
It is of academic necessity that we define a computer prior to exploring the theory of its
existence. The word computer is a derivative of the term compute which basically means to
calculate. So, in simple words, a computer is just a very complex calculator which “thinks” by
the way of logical calculations. The first computers were built to solve very large
calculations. As time progressed from the time of invention, computer functionality was
enhanced to incorporate various functions. Computers are electronic devices that follow
instructions to accept input, process that input, and produce desired output.
Figure 1.1.1: Computer processing cycle
A computer is a programmable machine, it allows the user to store all sorts of information
and then ‘process’ that information, or data, or carry out actions with the information, such
as calculating numbers or organising words.
The Development of Computers
Today’s computers have developed in a natural progression from the earliest calculating
aids used many hundreds of years ago. However, over the last five decades their
development can only be described as phenomenal.
We can go back over 5000 years to the abacus, which even in this present age is still in use
(sometimes by little children as an aid to counting in kindergarten school).
Figure 1.1.2: Abacus
This device consists of rods, which have beads strung over them, and which may be moved
from side to side, when performing calculations. It was claimed that a skilful operator could
work out sums faster with an abacus than someone using an electronic calculator.
Another significant development was the development of a machine known as
the difference engine around the 1820’s by Charles Babbage. Some people regard Babbage
as the father of computing. The machine was based on a mathematical method known as
‘differences’, which helped in speeding up mathematical computations. Unfortunately, the
technology of that time was unable to make the parts for the mechanical machine to the
degree of accuracy required.
Babbage was not deterred, and he proceeded to develop an even more sophisticated
machine called the analytical engine. It is considered that at this point the concept of the
modern computer was realised. Although it was not an electronic device, it had parts that
corresponded to the principal parts of a modern computer.
The advent of the Second World War saw tremendous development in computing.
Electricity was now being used to control the flow of information in computers, as opposed
to a strictly mechanical system.
First Generation Computer
When the vacuum tube/valve was invented, the important switching operations could be
carried out quicker and electronic versions were then produced. Computers using this
technology were known as first generation computers. During this time, they were mainly
used by the military to crack secret codes. A machine known as ENIAC (Electronic Numerical
Integrator Automatic Computer) was used in 1946 to correctly perform the following
calculation: 97,367 x 97,367 x 97,367 x 97,367 It performed this calculation in less than half a
second. This was considered really impressive at the time. To accomplish this feat, ENIAC
was made with 18,000 vacuum tube/valves, and needed to be housed in a room the size of
a school hall. The first computers to allow a program to be stored in memory was EDSAC,
developed at the University of Manchester. The vacuum tubes were fragile, subject to
overheating and caused frequent breakdowns.
Figure 1.1.3: EDSAC Computer
Second Generation Computer
Due to the shortcomings of the vacuum tube/valve technology such as overheating,
unreliability, and space requirement, more efficient components were sought. This led to the
development of the transistor in 1948 and it quickly replaced the vacuum tube/valve, which
had been used in the computers of the 1940’s and 1950’s.
The Introduction of low-cost and reliable transistors allowed the computer industry to
develop at a tremendous rate during the late 1950s. The cost and size of the machines was
radically reduced so it became possible for large commercial organizations to make use of
computers. Example of such machines include LEO III, UNIVAC and ATLAS.
(a) (b) (c)
Figure 1.1.4: (a) LEO III, (b) UNIVAC, (c) ATLAS computer
Third Generation Computer
In the mid – 1960s it soon became possible to place several transistors on a single base in
what is known as an Integrated Circuit (IC). The silicon chip in which integrated circuit
technology was used resulted in the production of even smaller, faster, more efficient and
reliable computers such as those of the IBM 360 series. These were known as third
generation computers.
Figure 1.1.5: IBM 360 Computer
Fourth Generation Computer
Today it is possible to pack millions on to just one. This has resulted in further giant strides
in computer development, utilizing what is referred to as Large Scale Integrated Circuit
technology (LSI), this made possible the development of a microprocessor, which in turn
enabled the production of the microcomputer. All computers used today make use of such
silicon ‘chip’ technology
(a) (b) (c) (d)
Figure 1.1.6: (a) IBM 5150, (b) SPARCstation, (c) Desktop_personal_computer, (d) Crystal
Project computer
Fifth Generation
At present most computers are still of the fourth-generation variety. Developments are
continuing towards expanding memory size, using Very Large-Scale Integration (VLSI)
techniques and increasing the speed of processors. This increasing power is allowing the
pursuit of new lines of development in computer systems:
Fifth generation computing devices, based on artificial intelligence, are still in development,
though there are some applications, such as voice recognition, that are being used today.
The use of parallel processing and superconductors is helping to make artificial intelligence
a reality.
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Video @Digital Birol: Fifth Generation Computers.
1.2 Types of Computers
Computers can be broadly classified into microcomputers, mini-computers, mainframes and
supercomputers. This broad categorisation is rather inadequate as there are quite a few new
terms in the field and you will need to update yourself on other categories available.
However, these categorisations are based upon the computer’s size and processing power.
Mainframe Computer
Mainframe computer systems are the largest and most powerful type of computer and are
used by large organisations such as banks, airlines and government departments. They
usually support a large numbers and variety of peripherals and can process a number of
applications concurrently. This is called Multi-programming. The mainframes power stems
from the phenomenal speeds of the processor and the large size of the main memory.
Mainframes may also be used for Wide Area Networks.
Mainframe computers are generally accommodated in special – purpose, air conditioned
rooms to ensure trouble free operation. Mainframe computers allow several peripheral
devices to be connected to them that is why they are ideal for research institutes where
multi tasking is essential.
Figure 1.2.1: Mainframe Computer
Minicomputer
This is a Mid-sized computer that fits between microcomputers and mainframes or servers.
Because of the power and price of microcomputers and the power of mainframes and
servers, minicomputers are no longer produced.
Minicomputers are scaled down version of mainframe computers. The
division between the two types becomes rather blurred when
referring to small mainframes and large minicomputers. Costing less and being robust
enough to operate without a special environment, they can be used in real-time
applications such and controlling manufacturing processes in an engineering company.
They are also used by medium sized organisations for all their processing needs of by large
organisations as part of a network.
Minicomputers can support a number of applications concurrently and are often used with
time – sharing operating systems and intelligent terminals to provide organisations with
decentralised processing facilities.
Microcomputer
This is the modern day PC (personal computer) The increase in
processor speed memory capacity and the facility for network (for multi – users operation)
now permits their user for multi tasking (the running of several tasks concurrently by one
user) Microcomputers are used in Local Network to allow sharing of disk and printer
facilities, as well as electronic communications between users (Electronic mail).
The low cost of microcomputers and the increase in the range of software available, makes
their use possible in almost any size and type of organisation. In a small firm, a
microcomputer may be used of word processing, stock control, costing, and general
accounting.
Supercomputer
This is a large computer or collection of computers that act as one large computer capable
of processing enormous amounts of data. Supercomputers are used for very complex jobs
such as nuclear research or collecting and calculating weather patterns.
IBM Blue Gene P supercomputer
Source: Wikimedia
1.3 Identify the main components of a computer
The computer components can be divided into four functional component groups of which
most are hardware parts – these are the physical parts of a computer that can be seen and
touched; Input Components, Processing Unit Components, Output Components and
Storage Components. Each of these components plays a major role in the computer and is
described below;
a) Input Components: - These comprises of devices used for input of data into the
computer, these devices are for getting the information into the computer and include
Keyboard, mouse, joystick, touch-pad and track ball, touch – screen, scanners, bar-code
reader, light pen etc.
b) Processing Unit Components: - The major component involved in this unit is the
Central Processing Unit (CPU). Data and instruction are executed here and manipulated to
produce the required information. The processor is made of three sub–components which
ensure the correct execution of data. Besides the CPU the main memory is also considered
to be one of the processing components as well as the computer’s motherboard but it must
be noted that the CPU is the main processing component here.
The CPU also known as a processor or microprocessor was first developed by Intel in 1974
and is short for Central Processing Unit. The computer CPU is responsible for handling all
instructions and calculation it receives from other hardware components in the computer
and software programs running on the computer.
The CPU has two main components:
The CU (Control Unit) which is responsible for issuing out control signals to other
parts of the computer system
The ALU (Arithmetic Logical Unit) which is responsible for all arithmetic and logical
“thinking” operations.
The CPU exists as an integrated chip which is small piece of semi-conducting material (such
as silicon) about 1 centimetre (¼ inch) square on which an integrated circuit is embedded.
An integrated circuit is a number of electronic components joined together to form a path
for electricity. Central processing unit chips contain the circuits representing the CPU.
The memory, the CPU and internal drives are found on a circuit board called the
Motherboard. The Motherboard is enclosed in the System unit. So the system unit is the box
containing the essential computer hardware devices other than the peripheral devices.
b) Output Components: - These are components which produce the results of the
processing in a human sensible format such visual displays, hard copy print out etc. They
include a monitor, printer, speakers, projectors, etc.
c) Storage Components: - These are devices and media for storing or keeping pieces and
programs in a computer system. Two types are available; primary and secondary storage.
Primary storage also known as the main memory helps in the computer’s internal storage,
all the data to be processed and computed by the computer must be stored in the main
memory. It is a storage location that holds memory for short periods of times while it I
being processed in the CPU. The RAM and ROM is an example of a primary storage device.
ROM
Short for Read-Only Memory, ROM is a type of memory that is capable of holding data
and being read from; however, it is not capable of being written to or having its data
modified. Unlike RAM, ROM is capable of keeping its contents regardless if it has power or
not. ROM is non-volatile. ROM is used by the computer to store start up programs like BIOS
(Basic Input Output System) otherwise known as ROM. BIOS is the one responsible for all
the computer device configuration.
RAM
Short for Random Access Memory, RAM, also known as main memory or system memory, is a
term commonly used to describe the memory within a computer. Unlike ROM, RAM
requires power; if power is lost, all data is also lost (it is volatile). RAM is the working storage
of the computer and its primary function is t
