INTRODUCTION
SRILANKA COMPUTER COMPETENCY LICENCE
(SLCCL)
Data and Information
Data is a collection of raw unprocessed facts, figures, and symbols.
Computers process data to create information.
Information is data that is organized, meaningful, and useful.
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0806973587
0806992867
1402748124
0831110848
Characteristics of Information
Following characteristics are important to identify information.
• Relevant to the purpose
• Sufficient to the purpose
• Clear to the user
• Should be timely available
• Should be worthwhile
• Communicated to the right person
A system has three stages
• Something feeds into the system (the input)
• The system does something with the input (the process)
• The process gives a result (the output)
What is a Computer ?
A computer is an electronic device that stores
and processes information according to a set
of instructions.
Advantages of Computers
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Accuracy
Speed (faster)
Undertake complex processing
Stores large volume of data/information
Cheaper in terms of processing data compared with manual
processing
Disadvantages of Computers
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Expensive (Cost of buying and maintenance)
It creates unemployment
It is human dependent
It is also highly dependent on external power
History of the Computer
ABACUS - supposed to be the first machine people used for
mathematical calculations, has been used over thousands of
years by various nations in the world to facilitate their
calculations.
Many people believe that Abacus is the foundation
of the modern computer
Pascaline - 1642, a French mathematician called Blaise Pascal
invented the adding machine that helped mathematical
calculations further.
Additions and subtractions could be done easily using this
machine. This machine is also called the “Pascaline”
An Englishman called Charles Babbage designed the first model
required for a mechanical computer in 1822.
It was called the ‘Difference Engine’
A French man called Joseph Jacquard designed a machine called
the ‘Mechanical Looms’ to help weaving cloths. He was able to
make various designs on cloths by using the cards with punch
holes.
This motivated Babbage to design the
'Analytical Engine‘ in 1833. However, he was
unable to produce the analytical engine as he
wished with the available technology at that
time.
This analytical machine, had the necessary
components required for data input, storage,
processing and output inside.
Computers designed later were greatly
influenced by these concepts of Babbage
and that is why Babbage is considered to be
the ‘Father of the computer’.
Charles Babbage
• A friend of Babbage called Ada Augusta Lovelace was keen on
preparing programmes required for his engine. Such
programmes are considered to be the first attempt of
computer programming. So, Ada Augusta Lovelace is
considered to be the first computer programmer in the world.
The computer language which was used later for military
purposes was named Ada to pay respect for her.
Howard Aiken and his friends in IBM Corporation in Harvard were
able to design a machine called ‘Automatic Sequence
Controlled Calculator’. However, it was later named as ‘Mark I’.
Mark I machine had the capability to carry out additions, subtractions, multiplications
and divisions very easily.
A type writer was connected to input data while punch cards were used for data
output. There were more than 3,000 electromechanical relays in Mark I and it was
about 5 tons in weight.
Mark I was used for more than 15 years in the world of computer.
A mathematician called John Von Neumann introduced the
concept of a computer to get different work done by using its
stored programs without making any physical changes to the
computer machine.
This concept of John Von Neumann is being used in the modern
computers.
Moor School of Electrical Engineering of the University of
Pennsylvania produced the world’s first electronic digital
computer in 1946.
This was called ENIAC (Electronic Numerical Integrator and
Computer) and about 18,000 vacuum tubes were used to
develop this machine.
ENIAC computer was able to carry out about 5,000 calculations
within a second,
Drawbacks were
the large size of the machine, the frequent changes of burned
vacuum tubes due to excessive heat and the high electrical
consumption.
Computers which were designed using vacuum tubes are called
the ‘First generation computers’.
In 1950, Remington Rand institution manufactured
UNIVAC - I (Universal Automatic Calculator - I) computer which
had the capacity to carry out about 10,000 calculations in a
second.
In 1957, International Business Machine Corporation
(IBM) designed its ‘IBM 704’ computer which could
carry out about 100,000 calculations per second.
The second generation of computers was started with the
invention of the Transistor. The honour of inventing the
transistor goes to William Shockley, John
Bardeen and Walter Brarttain of the Bell Laboratory.
Computers in this generation were designed with smaller
transistors and these computers could perform 200,000 –
250,000 mathematical calculations per second.
Low electrical consumption and smaller
size were the key characteristics of the
second generation computers.
Third generation computers were designed with the
Integrated Circuits (IC )
Micro-chips which were designed with the development of the
technology represent the fourth generation of the computer.
These microchips are called microprocessors too.
Classification of Computers
Super Computers
Mainframe Computers
Mainframe computers
are typically:
Powerful - they can
process vast amounts
of data, very quickly
Large - they are often
kept in special, airconditioned rooms
Multi-user - they
allow several users
(sometimes hundreds)
to use the computer
at the same time,
connected via remote
terminals (screens and
keyboards)
Mini or Midrange computers
They usually fall
in between
mainframe
computers and
microcomputers
• Micro Computers /Personal Computers
Desktop Computer
Laptop Computer
A 'laptop' computer is
a light, compact and portabl
e PC.
Laptops contain
a rechargeable battery so
that they can be used even
when not plugged in to a
mains power supply.
They also have a built-in
LCD monitor.
Personal Digital Assistant (PDA)
A PDA has no keyboard, uses
a touchscreen for all data input. Since the
screen is so small, many PDAs have a
small stylus (plastic stick) that is used to
press things on the screen.
Most PDAs use some sort of handwritingrecognition system to allow the user to
write on the screen, and have their
writing converted into text.
PDAs tend to be used a 'digital diaries'
allowing users to take their email, documents, appointments, etc.
with them wherever they go.
Tablet PCs