### Bank Clerical Computer Fundamental Study Material | Computer Study Material For Bank Clerical Preparation

1. What is a computer?
A computer is a tool or instrument that helps in computation. Computation includes addition,subtraction, multiplication, division, comparison of numbers, manipulation of texts, logicaldecisions etc. We use calculators in our routine for carrying out calculations. However, thescope of application of a calculator is thus very limited. A computer, in contrast, can store aseries of instructions and huge information and data in its memory and process a complete
job.Efficiency of the computer depends on the set of instructions given to it. It exactly does whatit has been told to do. Precise, clear and correct instructions should be given to the computer
to enable it to carry out the operations correctly. When the instructions are faulty and notclear, the results produced by the computer will also be faulty and not clear. This phenomenon of wrong output of data due to wrong input of instructions/data is termed as
Garbage in Garbage out (GIGO).
2. What are the advantages of computer?
• Very high speed processing
• Large capacity for storage and retrieval of data
• Perfect accuracy
• Automatic working capability
• Diligence
• Versatility
3. What are the limitations of computer?
• Can not think on its own
• Can not learn by experience
• Can not take independent decisions on its own.
• Requires human intervention for each any every step

4. Explain the evolution of computers.
Increasing need for numerical calculations, storage of data and information etc. with minimum of mental and manual efforts led to invention of computers.
• ABACUS, used for calculations, was the earliest devise that qualifies as a computer widely used 6000 years ago. The ABACUS was built using the idea of place values.
• John Napier developed Logarithm, a tabular system of numbers through which many arithmetical calculations were simplified, in 1617.
• Napier also invented a set of rods which were carved from bones and used for multiplication. These were called Napier Bones.
• Slide Rule, based on the principle of logarithm, a calculating device was invented by William in 1620.
• Blaise Pascal, a Frenchman, invented a mechanical unit in 1642 that could add and subtract, using a set of toothed wheels. This ‘calculator’ was the first digital machine.
• Pascal’s machine was further improved by a German mathematician Gottfried that could add, subtract, multiply, divide and extract roots.
• In 1822, Charles Babbage built the ‘Difference Engine’. This could do only one kind of calculations.
• In 1833, Charles Babbage designed and worked on Analytical Engine. It was a general purpose computer designed to solve almost any type of problem. It contained most of the elements we find in modern digital computer systems. Hence, Charles Babbage is considered as Father of modern computer.
• Joseph Jacquard invented punch cards in 1801. Punch card had holes punched in it. These were used by him to produce weaving pattern on the cloths.
• In 1880, Dr.Herman Hollerith used punched cards for data processing by building a tabulating machine that could punch holes in cards and read them as well. This machine worked on electricity and had mechanical parts and could handle 50 to 75 cards per minute. The system was very slow and card jams and data destruction were common problems. Punching machine, Verifying machine, Interpreter, Sorter, Collators, Tabulator were some of the machines used in this system.
• In 1944, Howard Alken built MARK1, the first digital computer, at Harvard University. It lacked speed but had the ability to continuously perform complex arithmetic functions
without frequent human intervention. It was partly electronic and partly mechanical machine.
• In 1936, Alan Turing from Cambridge University submitted his brilliant logical analysis on ‘artificial intelligence’. His contribution on the development of electronic computers remains the single biggest contribution ever made to the science.
• In 1930, Germans developed a mechanical machine called as ‘ENIGMA’ for coding militarymessages.
• In 1939, Britain initiated to build machines that could decipher Enigma’s codes. The world’sfirst giant computer using values was built called the ‘Colossus’.
• In 1942, USA started to develop an electronic computer. In 1946, it could put to operation ‘ENIAC’ (Electronic Numerical Integrator and Calculator), made in University ofPennsylvania. John Mauchly and J.Presper Eckert were the two people involved in its
development. This computer was made of 18,000 vacuum tubes. ENIAC could process the data at great speeds (though not comparable to today’s computers).
• UNIVAC‐1 was the first business oriented computer developed in 1952 used by US Bureau of Census.
5. Explain the ‘Generations of computers’.
A generation is a rough period of time over which there are no major changes or development in that particular field. Every change in technology has been treated as a new ‘generation’ of computers. Each generation has its own advantages and disadvantages.
First Generation Computers :
• Used vacuum tube technology. (Vacuum tube is a fragile glass device that can control and amplify electronic signals.)
• Computers were very large in size and generated lot of heat.
• Speed was measured in milli‐seconds.
• Developed many problems and required frequent maintenance.
• Performed at low speed, occupied large space, consumed more power and needed air conditioning.
• Example : ENIAC(Electronic Numerical Integrator and Calculator) computer developed by USA.
• EDSAC (Electronic Delayed Storage Automatic Computer) was another major development; developed at Cambridge University of England; first introduced in May, 1946.
• Advantages : Vacuum tube technology made possible the advent of electronic digital computers and these were the fastest calculating devices of that time.
• Disadvantages : Very bulky and non portable; lot of heat generated and so air‐conditioning compulsory; frequent hardware failures and maintenance.
Second Generation computers:
• Developed in late 1950’s.
• Used transistors in place of vacuum tubes. Transistors were smaller, less expensive and generated less heat compared to vacuum tubes.
• Speed measured in micro‐seconds.
• Magnetic tapes could be used as medium for storage of data.
• Example : UNIVAC (Universal Automatic computer) was the first commercial business computer
• Example : IBM 1401, IBM 1410
• Advantages : Flaws of first generation computers removed; smaller in size; Faster and more reliable; commercial production easier and cheaper.
• Disadvantages : Air conditioning required; Manufacturing process involved manual
assembly

Third Generation computers:

• Developed in mid 1960’s. (1965‐71)
• Used LSIC (Large Scale Integrated Circuits) in place of transistors. IC was small and one IC
could do the job of hundreds of transistors.
• Computers became smaller and faster
• Speed measured in nano‐seconds.
• Magnetic drums used as medium of storage of information.
• Led to development of software (called Operating System) for efficient use of computer.
• Example : IBM‐360 series introduced in 1964`
• Advantages : Smaller in size; more reliable and portable; low maintenance cost, lesser
power required.
• Disadvantages : Required highly sophisticated technology for manufacturing ICs.
Fourth Generation Computers:
• Introduced in 1970’s
• Used VLSI (Very Large Scale Integrated) Circuits containing thousands of transistors, diodes
and registers.
• Roughly more than 30,000 components could be accommodated on one chip of the size of
a postal stamp.
• Concept of micro‐processors evolved. It is a chip of silicon known as microprocessor chip.
• Could be easily placed on small table
• Price reduced and affordable and became a common equipment in small business establishments.
• Advantages : Size reduced substantially; air conditioning not required; operations much faster; more general purpose; cheapest amongst all previous generations; desktops made
available for business/personal use. Fifth Generation and next generation computers
• Based on ULSI (Ultra large scale integration) technology.
• Will have tremendous processing power and speed.
• Support high degree of artificial intelligence (computers will be able to think and learn and act on their own to some extent)
• Interact with humans in ordinary languages
Advantages : More user‐friendly; reduced size; easy to operate; economical and faster; programming much easier and simpler; emphasis shifted to networks and client server technology.
6. Explain the classification of computers.

Computers are classified into 3 broad categories basing on – type, purpose, capacity.
Type :
Analog computers : These are measuring devices that work on volatile data. Eg. Heat, pressure, humidity, speed etc. Eg. Thermometers, barometers, speedometers. These are sensitive to slightest changes.
Digital computers : Deal with numbers; can be used to manipulate data with great accuracy. Take input and give out put. Can store large quantities of data. Eg. All electronic computers, calculators, quartz watches etc.
Hybrid computers : Mixture of analog and digital computers. Input is generally in the form of analog form like heat/pressure etc., measured by analog part of computer and then used by digital part for further operations. Eg. Computers used in factories for controlling manufacturing processes, launching a rocket etc.
Purpose :
General Purpose computers : Capable of handling many kinds of operations. Used for both business and scientific applications with equal efficiency. Can be used at any place like offices, banks, schools etc.
Special Purpose computers : Designed to perform specific task and can not be used for other purposes. Eg. Monitor patient’s health in hospitals, in airports to monitor arrival/departure of flights etc.,
Capacity :
Super computers : Very large in size with very high processing speeds having more number of processing units. These are generally used for complex scientific computations / purposes.
Main Frame Computers : These are large computer systems having capability to support more powerful peripheral devices and terminals.
Micro computers : Micro computer is the smallest category of computers consisting of microprocessor
and associated storage and input/output devices.
Mini Computers : Relatively fast but small and inexpensive as compared to Main framecomputers. A mini computer can support 10 to 12 terminals.
Personal computers : Designed for personal use. Several models are available in the market.
These are very widely used and seen everywhere. Today these are available with very high
processing speed and large storage capacity at affordable prices.
7. Write about concepts of Number Systems and the data representation in computers.
As the computer is an electronic device, it works on the presence/absence of electronic signals. Electrical energy is used only to carry information.
Computer uses a number system which is different from our usual decimal system for storing data. It can just recognize two states – ON or OFF and numbers are represented by using these two states i.e., by using the ON position to represent ‘1’ and the OFF position to represent ‘0’. Therefore, a number can be simulated easily within the computer under a number system which uses two digits only i.e, ‘0’ and ‘1’. This system is called Binary system. In decimal system we use 10 digits from 0 to 9. Each decimal ‘digit’ takes one of these ten values. The value depends on the ‘position’ of the number system i.e, units, tens, hundreds, thousands and so on.
Binary Number system :
The binary digits (0 and 1) are used to represent data in a computer. In computer terminology, the binary digit is called as a ‘bit’. As the computer works on electricity, the number 1 represents power on and 0 represents power off. Computers do not understand letters of decimal numbers. They only understand 1s and 0s. This is called the binary system. All the letters of the alphabet, all numbers and all signs like +, ‐, = etc are converted into 0s and 1s if the computer has to work with them. The positional value of each digit has to be the power of 2 i.e., 24 23 22 21 20 etc. (i.e., 16, 8, 4, 2, 1 etc.). The base of decimal system is 10 where as the base of binary system is 2. So this is also called ‘BASE2’ number system. The base of numbering system is called ‘Radix’. Therefore, the Radix of decimal system is 10 and that of binary system is 2.

Decimal to binary conversion : The decimal number is successively by 2 (base of binary system) until division is no longer possible. At the end of each of successive division, the
remainder is written in the next column. The binary equivalent of decimal number is obtained

by writing the remainder from the bottom to the top.
Example : Find the binary equivalent of Decimal Number 30.

Base=2

Number=30

Remainder
2

15

0
2

7

1
2

3

1
2

1

1
0

1

Binary equivalent of 30 = 11110

Binary to decimal conversion : Write down the place value of binary numbers, multiply the place value with the number and add the result so obtained to get the value in decimal system.
Example : Convert the binary number 1110010 to decimal.

b) 64 32 16 8 4 2 1 Place value in decimal system
c) 1 1 1 0 0 1 0 Binary number given in the example
d) 64 32 16 0 0 2 0 Multiply (b) & (c) = b X c to get place values
e) 64 + 32 + 16 + 0 + 0 + 2 + 0 Add the place values to get decimal equivalent
Answer : 114 in decimal number system

We can also perform addition, subtraction, multiplication and division functions in binary system. The following examples illustrate them :

Addition : Basic rule is – when we add two1’s the result is 0 with a carry digit.

 10101 +10101 1000001 +100001 111110 +11111 10101 100000 111110 +10101 +100001 +011111 101010 1000001 1011101

Subtraction : This can be performed by using the process of addition by adding the complement of the number to be subtracted to the number from which subtraction is to be made. The complement is obtained by either using 1’s complement or 2’s complement.
By using 1’s complement : 1’s complement is obtained by changing all the 0’s to 1’s and vice versa. Eg. 1’s complement of 10001 is 01110. The left most digit is treated as sign bit i.e, ‘0’ is +ve and ‘1’ is –ve.
Procedure :
a) Obtain the 1’s complement of the number which is to be subtracted
b) Add the numbers and add the carry bit in the result.
Example : Subtract 01000 (8 in decimal system) from 01100 (12 in decimal system)
1’s complement of 01000 : 10111
Now add 01100+10111 : 1 00011 (1 placed at distance is carry bit)

00100 (4 in decimal system)

====
As the left most bit is ‘0’, the answer is ‘+ 4’
By using 2’s complement : 2’s complement is obtained by adding ‘1’ to the 1’s complement.
Eg. 2’s complement of 10001 is 01111 (01110+1=01111)
Procedure :
a) Obtain 2’s complement of the number to be subtracted
b) Add the numbers and neglect the carry bit.
Example : Subtract 01000 (8 in decimal system) from 01100 (12 in decimal system) 2’s complement of 01000 is 10111+1 = 11000
Add 01100+11000 = 1 00100 (carry bit ‘1’ is neglected)
As the left most digit is ‘0’, the answer is ‘+ 4’ (00100 = 4 in decimal system) Similarly, we can perform multiplication and division operations in binary system.
Octal number system :
The number system is based on 8 digits i.e., from 0 to 7. Therefore, it is called as Base‐8 number system. This system is used by computer designers/engineers. We can get the octal equivalent of a decimal number by dividing the decimal number successively and remainders written from bottom to top. Eg. Octal equivalent of decimal number 135 = 207.
Hexa‐Decimal System :
This number system is based on 16 elements. The first 10 digits form from 0 to 9 and the 11th to 16th elements are represented by A,B,C,D,E,F. Therefore 10 in decimal system is equal to A

in hexa‐decimal, 11 is B, 12 is C and so on. This systems is also known as Base‐16 number
system. This system is used by system designers.The equivalents of some decimal numbers in
hexa decimal syster are as under :

 Decimal Hexa‐decimal 26 1A 27 1B 28 1C 29 1D 30 1E 31 1F 32 20

Bits & Bytes : Each 1 or 0 that a computer understands is called a bit. A group of 8 bits is called a byte. All letters, digits and signs are stored in the computer as bytes. The standard by which all characters (numerals, alphabets, symbols) are represented by a combination of 1s and 0s is called ASCII (American Standard Code for Information Interchange). Computers all over the world understand characters written in ASCII format. A combination 8 bits is used for representing any single character in this system. Thus the system could provide a total of 28 = 256 unique combinations. Thus a table of 256 codes was prepared and the code was assigned to each character. The codes were numbered from 0 to 255. Earlier computers used the 8 bit word. Today’s computers use 16‐bit to 64‐bit words.
Binary Coded Decimal (BCD) : Each decimal digit in a binary code is assigned a four‐digit binary code to avoid the task of converting the numbers as a whole into binary. This code is known as BCD. This occupies more storage space than in pure binary system.
Memory Storage : This is measured in bytes.
• 1 kilobyte (KB) is equal to 1024 bytes
• 1 Megabyte (MB) is equal to 1024 KB (10,48,576 bytes)
• 1 Gigabyte (GB) is equal to 1024 MB (107,37,41,824 bytes)
8. Explain the ‘hardware’..
Hardware is the term given to the physical components of the computer system and various individual pieces of equipment. Thus the key board, monitor, mouse, printers etc., all come