The document discusses the five generations of computers based on the underlying technologies used. The first generation used vacuum tube technology, while the second generation introduced transistor technology. The third generation was based on integrated circuit (IC) technology, and the fourth generation used microchip technology. The fifth generation aims to develop computers with human-like thinking capabilities using technologies like ultra-large-scale integrated circuits and artificial intelligence. The document also covers other classification methods of computers like by purpose, size, and operating principles.

1. 1. GENERATIONS OF COMPUTERS:
The tem generation indicates the type of technology used in the
computer construction. As new technology was emerging, it was
being used in the making of computer. The new technology improved
the speed, accuracy and storage capacity of the computers.
Different technologies have been used for computers in different
times.
Therefore, computers can be divided into five generations
depending upon the technologies used. These are:
First Generation (1942 – 1955)
Second Generation (1955 – 1964)
Third Generation (1964 – 1975)
Fourth Generation (Since 1975)
Fifth Generation (Since 1980)
1. First Generation Computers (1942 – 1955):
The vacuum tube technology was used in first-generation
computers. Mark-1m, ENIAC, EDSAC, EDVAC, UNIVAC-1 etc.
machines belong to the first generation of computers. The machine
language only was used in first-generation computers.
Principle:-
The vacuum tubes consisted of filaments inside it which on heating
emit electrons. These electrons were responsible for the
amplification and deamplification of electrical signals.
Input:-
Punched cards
Output:-
Print-outs
Advantages:

2. *These computers were the fastest of their time.
*They were programmed using machine language.
*The electronic digital computers were introduced due to the
vacuum tube technology.
Disadvantages:
*Very large in size
*Not reliable
*Consumed large amount of energy
*Constant maintenance required
*More heat generated and air-conditioning was required
*More costly
*Very slow in speed (data processing)
*It was difficult to programmed, because they used only machine
language
*Non-portable
*Limited commercial use
2. Second Generation Computers (1955 – 1964):
The transistor technology was used in second-generation
computers. The electronic component transistor was invented in
1948 at Bell Laboratories. The transistor is smaller in size and
more reliable than vacuum tube. Therefore, the transistor
technology was used in computer in place of vacuum tube
technology. The programming assembly language was also introduced
in second-generation of computers.
The transistors consisted of BASE, COLLECTOR and EMITTER.
Their functions include:-
BASE: input gate for the transistor.
COLLECTOR: collect the amplified signals
EMITTER: output gate for emitting the amplified signals to the
external environment.

3. Advantages:
*Low in cost
*Smaller in size
*Fast in speed
*Less heat generated more reliable and accurate in calculations
*Consume low power etc.
*Used for commercial purposes
*Portable
*Assembly language was introduced. This language is easy to write
program than machine language
Disadvantages:
*Air-conditioning required
*Commercial production was difficult and these were very costly
*Constant (or frequent) maintenance required
*Only used for special purposes
3. Third Generation Computers (1964 – 1975):
The IC (Integrated Circuits) technology was used in third-
generation computers. In a small IC chip (5 mm square size) a
circuit is designed having large number of electronic components
like transistors, capacitors, diodes, resistors etc. Initially, an IC
contained only about ten to twenty components. Thus the IC
technology was named as Small Scale Integration (SSI). The third-
generation was based on IC technology and the computers were
designed using this technology.
Advantages:
*Smaller in size
*Production cost was low
*Very fast in computational power

4. *More reliable
*Low power consumption
*Maintenance cost was low because failure rate of hardware was
very low
*Magnetic disk, used for external storage
*More storage capacity
*Easily portable
*Easy to operate
*Upgraded easily
*Widely used for various commercial applications all over the world
*Lower heat generated
*High-level languages were commonly used
*Many input/output devices were introduced such as mouse and
keyboard etc.
Disadvantages:
*Air-conditioning required
*Highly sophisticated technology required for the manufacturer
chips
4. Fourth Generation Computers (1975 onwards):
The microchip technology was introduced in this generation of
computers. With the advancement in IC technology, LSI (Large
Scale Integration) chips were developed. It was possible to
integrate over 30,000 or more components on to single LSI chip.
After LSI, the VLSI (Very Large Scale Integration) was developed
and the development of microprocessor possible. It is expected
that more than one million components will be integrated on a single
chip of VLSI. Using VLSI technology, the entire CPU is designed on
a single silicon chip. The use of microprocessor as CPU introduced
another class of computers called the microcomputers. Thus
fourth-generation may be called Microcomputer generation. IBM

5. introduced its personal computer for use in 1981.
Advantages:
*Smaller in size
*Production cost is very low
*Very reliable
*Hardware failure is negligible
*Easily portable because of their small size
*Totally general purpose
*Air conditioning is not compulsory
*Very high processing speed
*Very large internal and external storage capacity
*Used advanced input & output devices such as optical readers,
laser printers, CD-ROM/DVD-ROM drives etc.
Disadvantages:
*Highly sophisticated technology required for the manufacturer of
microprocessor chips
5. Fifth Generation Computers (In process):
The main drawback of first to fourth generation computers is that
the computers have not their own thinking power. These are totally
depending upon the instructions given by the users.
Fifth generation computers are supposed to be the ideal computers,
but do not exist. The scientists are working to design such
computers that will have the following features.
*Having their own thinking power
*Making decisions themselves
*Having capabilities of learning
*Having capabilities of reasoning
*Having large capacity of internal storage

6. *Having extra high processing speed
*Having capabilities of parallel processing
Technologies used in fifth generation computers:
*ULSIC (Ultra Large Scale Integrated Circuits) technology
*Artificial Intelligence (AI) technology also called the knowledge
Processor. The AI means automatic programs that let the machines
to think and decide themselves. The programming languages LISP
(List Processor) and PROLOG (Programming with Logic) are used for
artificial intelligence. The scientists at ICOT in Japan use the
PROLOG to develop the Artificial Intelligence software.
Advantages:
*Laptops, Pocket computers and PDA were developed.
*Development of parallel processors
*Development of centralized servers
*Development of optical disc technology
*Invention of internet and its advantages.
2. CLASSIFICATION OF COMPUTERS:
Computers can be classified based on the following criteria:
According to Technology:
$Analog Computers
$Digital Computers
$Hybrid Computers
According to Purpose:
$General purpose Computers
$Special Computers
According to size:
$Supercomputers

7. $Mainframe Computers
$Minicomputers
$Microcomputers, or Personal Computers
Based on operating principles and technology:
Analog computers:
$These computers represent data in the form of continuous
electrical signals.
$These are fast and multi-tasked.
$Results displayed by these computers are less accurate.
$Powerful in solving differential equations.
$These computers use OP-AMP (Operational Amplifier).
$The features of OP-AMP include:
*High voltage gain. The voltage gain is defined as the ratio of
output voltage to input voltage.
*Infinite input resistance. The input resistance is defined as the
ratio of change in input voltage to the change in input current.
*Zero output resistance. The output resistance is defined as the
nominal resistance measured with nil loads.
$The basic OP-AMP circuit is represented as:
Wherein, Rin is the input resistance, RF is the feedback resistance
A is the amplifier which is used to invert the incoming signals of

8. voltage Vin to Vout.
Digital computers:
$These are called the Digital information processing systems.
$These systems store and process the data in digital form (strings
of 0's and 1's)
$They are capable of processing analog signals but the analog
signals have to be converted into digital signals using an ADC
before feeding into the digital computers.
Hardware components:
$Arithmetic Logical unit (ALU)
$Control unit
$Memory unit
$Input unit
$I/O units
Hybrid computers:
$These are the combination of both Analog and Digital computers
encompassing the best features of both the computers.
$Fast, efficient and reliable computer systems.
$The Data is measured and processed in the form of electrical
signals and stored with digital components.
$The input is accepted in the form of varying electrical signals and
is converted into discrete values for performing operations.
$They are used in hospitals to measure heartbeat and have
engineering and scientific applications.
Based on Applications:
General purpose computers:
$Work in all environments
$Versatile computers
$Store number of programs to perform distinct operations

9. $More expensive
$Not efficient and consume large time to generate results
Special purpose computers:
$Work on specific tasks
$Non-versatile
$Speed and memory of these computers depend on the task
performed
$More efficient and consumes less time to process results
$Less expensive
Based on size and capability:
Micro-computers:
$These are small cheap digital computers for individuals
Hardware components:
Microprocessor, storage unit, I/O channels, power supply,
connecting cables.
Software components:
Operating System (OS), Utility software, Device drivers
Available in the forms of:
PC's, Work stations, Notebook computers.
The various components are:
Microprocessors:
$This incorporates all functions of the CPU into a single unit. The
various units of microprocessor are:
$ALU: performs arithmetic and logical operations.
$Registers: Store data and instructions temporarily needed by the
ALU.It includes several types like: Accumulator (ACC), Program
Counter (PC), etc.
$CU: Control unit-Used to manage and control the functions of
microprocessors, I/O devices

10. $Memory:
Used to store data and instructions. It is of two types:
*Primary memory: It stores temporarily the data and instructions
needed by the microprocessor
*Secondary memory: It stores data permanently. Examples include
magnetic tapes, floppy, CD, USB, etc,
Peripheral devices:
$Input devices: They are used to transfer data into the
computer. Examples: keyboard, mouse, etc,
$Output devices: Used to display the results processed by the
computer. Examples: Monitor, printer, etc,
System bus:
$It is also called the FRONTSIDE BUS, MEMORY BUS, LOCAL or
HOST BUS.
$It is used to connect microprocessor, memory and peripheral
devices into a unit.
SYSTEM BUS= ADDRESS BUS+DATA BUS+CONTROL BUS
$Address bus: Unidirectional bus to identify the peripheral devices
and memory.
$Data bus: Bi-directional bus used to transfer data among the
microprocessor, peripheral devices and memory.
$Control bus: bus used by the microprocessor to send control

11. signals to various devices.
Depending on size, Microcomputers are of three types:
*Desktop computers:
They are used in single location, cheap, and have good storage.
Examples include: Apple, IBM.
*Laptop computers:
Portable computers also called as the notebook computers or mobile
computers. They are smaller in size, more expensive and are
rechargable.Examples include Apple, Acer, Hewlett Packard (HP)
*Hand-held computers:
Also called as Personal Digital Assistants (PDA's), Palmtop or
Mobile device. They are smaller in size, have smaller display and
input device is generally an electronic stylus. Their storage
capacity is small. Examples include Apple Newton, Franklin eBook
man.
Mini computers:
$These were introduced by Digital Equipment Corporation (DEC) in
1960.
$They can process more data and can support more I/O devices
They are less powerful than mainframe computers but more
powerful than micro computers. Hence they are called MID-RANGE
COMPUTERS.
They cater to the needs of 4-200 users at a time
$They are used in business as a centralized computer or as an
internet server
$They are less expensive than Mainframe computers. Examples
include PDP 11, IBM 8000 series, etc,
Mainframe computers:
$These are capable of handling millions of records a day.
$These are bigger and more expensive than mini-computers

12. $They require a large space and closely monitored humidity and
temperature.
Characteristics:
*A typical mainframe computer consists of 16 microprocessors and
even more than that.
*RAM capacity is 128MB to 8GB
*They can run multiple operating systems. Hence they are called-
VIRTUAL MACHINES
*They handle a large amount of I/O devices which are arranged in
separate CABINETS or FREMES and hence the name.
Applications:
*they are used in large financial transactions
*Enterprise Resource Planning (ERP)
*Industry and consumer statistics
*Census
Supercomputers:
$These are the fastest and complex computers with very high
speed
$First Supercomputer was presented by SEYMOUR CRAY in 1960 in
Control Data Corporation (CDC)
$Used exclusively in applications where large complex calculations
have to be performed to get the output
$These are very expensive and designed to perform only small
number of programs at a time
$The manufacturers of Supercomputers are: IBM, SILICON
GRAPHICS, FUJSTU, INTEL, etc.
These are the fastest as they employ 1000's of processors, 100’s
of GB of RAM, 1000’s of GB of secondary storage
$the principles used in these computers are:
*Pipelining: This enables the processor to execute second
instruction even before the first is completed provided, it has the
required resources

13. *Parallelism: Enables the processor to execute several instructions
at a time
$Examples include: CRAY 3, Cyber-205, PARAM, etc.
3. Characteristics of computers:
Computers have distinguishing characters which make them ideal
machines. But they do not certain characters which human possess.
Some of the important characteristics of computers are:
(I)Automatic:
#Computers are automatic machines which once started a job,
carry it on until it is complete provided they are given the required
instructions by the users.
(II)Speed:
#The computers are capable of taking logical decissions,
performing arithmetic and non-arithmetic operations on alphabets
and copying at an unbelievable speed
#The units of speed for a computer are in microseconds (10 -6) or
even in nano and Pico second (10 -9 or 10 -12)
#A powerful computer can perform 3 to 4 million arithmetic
operations per second
#The speed of the computers is attributed to the fact that THE
COMPUTERS ARE ELECTRONIC DEVICES WORKING ON
ELECTRICAL PULSES WHICH TRAVEL AT HIGH SPEED.
(III)Accuracy:
#The computer produces highly accurate and reliable results
#The errors in the calculations may be due to the error in the
logic of the human but not due to the computer.
#The computers perform accurate calculations 'n' number of times
(IV)Versatility:
#A computer is capable of performing a wide variety of functions

14. #It can accept data and produce results.
#It can perform the basic arithmetic and logic operations
#It can transfer data internally
#Several applications can be run at a time. For example MS paint
Adobe Photoshop and VLC media player can be run at a time.
(V)Diligence:
#A computer is capable of performing the same task over and over
again with the same degree of accuracy and reliability as the first
one
#This is because, unlike human beings, computers are free from
monotony, tiredness, lack of concentration, etc, and can work
hours together without creating bugs.
(VI)Large and perfect memory:
#A computer can store and recall any amount of information
because of its secondary storage capability with perfect accuracy
unlike human beings.
#The storage capacity of the computer is enormous and is perfect
#A computer recalls a data with greater accuracy even after
several times and does not lose any information unless it is
prompted to do so.
(VII)No I.Q and feelings:
#A computer is not intelligent on its own and cannot think on its
own
#It can only perform the tasks specified by the human but the
difference is that it does this with greater accuracy and speed.
#It cannot decide on its own and only the user can determine what
the computer must do
#A computer has no feelings but a human does.
4. Basic computer organization:

15. The organization of computers involves the interfacing of various
components of the computer and the co-ordination of the
operations performed by them. The various functional units of a
computer include:
(I)Input unit
(II)Memory unit
(III)Central processing unit
(IV)Output unit
BASIC COMPUTER ORGANISATION
Input devices:
@These devices are used to feed the data inside the computer.
@The most commonly used input devices are:
*keyboard
*mouse

16. *light pen
*digitizer
*trackball
*joystick
*OCR (Optical Character Recognizer)
*MICR (Magnetic Ink Character Recognizer)
*OMR (Optical Mark recognizer)
Keyboard:
@It is used to enter alphanumeric data into the computer and to
perform special functions:
@Alphanumeric keys: Used to enter alphabets and Numbers
@Function keys: Used to perform special functions. These include
F1 to F12.For example F5 is used for refreshing a page or desktop
@Modifier keys: SHIFT and CONTROL keys are called modifier
keys and they perform special functions. For example CTRL+X for
cut
@Spacebar key: Used to move by one space in a document or
worksheet or DBMS.
@Enter key: Used to open something like a file or a web-page or
to move to the succeeding line in a document.

17. Mouse:
@It is an electronic device used for selecting and pointing
purposes. Hence it is called the POINTING DEVICE.
@Left mouse button: Used for selection purpose
@Right mouse button: Used to perform special functions like OPEN,
EXPLORE, COMPRESS, etc.
@Ball at the bottom: The ball at the bottom of the mouse moves
and the cursor moves on the screen in whichever direction the ball
rotates
@Wheel at the top: To scroll a web-page or a document.
Scanner:
@Used to scan images and documents
@The scanned images are converted into the DIGITISED IMAGES
understandable by the computers.
@Color images can also be scanned using the scanner depending
upon the RED GREEN BLUE (RGB) PROPORTIONS
@The principle used in the BARCODE READER is similar to that of
a scanner.
Memory unit:

18. MEMORY PYRAMID OF A COMPUTER
The memory unit is used to store data on a temporary or
permanent basis. The various types of memory can be depicted as:
0100090000032a0200000200a20100000000a201000026060f003a0357
4d464301000000000001007a8e0000000001000000180300000000000
018030000010000006c00000000000000000000001a000000370000000
000000000000000b63100006418000020454d46000001001803000012
00000002000000000000000000000000000000f6090000e40c0000d800
0000170100000000000000000000000000005c4b030068430400160000
000c000000180000000a00000010000000000000000000000009000000
10000000de050000e1020000250000000c0000000e000080250000000c
0000000e000080120000000c0000000100000052000000700100000100
0000d2ffffff000000000000000000000000900100000000000004400022
430061006c006900620072006900000000000000000000000000000000

19. MEMORY:
PRIMARY MEMORY

20. @Read only memory
*MASK PROM
*PROM
*EPROM
*EEPROM
@Read/Write memory
*Static RAM
*Dynamic RAM
*Cache memory
SECONDARY MEMORY
@Disk Drives
*Floppy
*Hard disk
*CD-ROM (Read only and Rewritable)
@Tape drives:
*Cartridge Drive
*Cassette drive
INTERNAL PROCESSOR MEMORY
@Registers
*ACC
*PC

21. *IR
*MAR
*MBR
*MDR
Primary memory:
@This memory is also called as MAIN MEMORY.
@The information stored in this memory that are needed by the
microprocessor during the time of processing are temporary and
the information in the ROM are permanent
Read Only Memory (ROM):
@It is a non-volatile memory
@The contents of this memory are permanent
@These are cost-effective
@They are available in high storage capacity
@Processing speed is very low
@Generally, the OS supporting programmes and the Basic Input
Output System (BIOS) programs are stored in this
@In this trigonometric and logarithmic functions are also stored
@In PROM (Programmable Read Only Memory), The flexibility of
data alteration is also provided.

22. Random Access Memory (RAM):
@This is the part of computer's temporary storage where the ALL
THE DATA, INSTRUCTIONS NEEDED BY THE MICROPROCESSOR
AND THE RESULTS EXECUTED BY IT are stored.
@It is a volatile memory
@The contents are temporary
@Cost is very high
@They are available in small storage capacity
@processing speed is high
@User defined programmes can be stored at any time
Principle:-Each bit in a RAM stores information by means of
electric charge, where the presence of electrical signals indicate'1'
and the absence of electrical signals indicate'0'.
Types of RAM:
DYNAMIC RAM:
@The electric charges tend to be leak out in a few milliseconds, so
the information present in RAM is lost
@Hence, the set of data stored in Dynamic ram has to be
refreshed periodically before all the charges have leaked.
STATIC RAM:

23. @Special refresh circuitry is provided
@They are not leaky and hence do not require any refreshing
Cache memory:
A small memory between the CPU and the main memory is called
the cache memory.
@It is faster than main memory and the access time of this
memory is close to the processing speed of the CPU
@It acts as a HIGH-SPEED BUFFER between the CPU and the
main memory
It is used to store temporary and active (most frequently used)
data during the time of processing
The other components of primary memory include:
@PROM (Programmable Read Only Memory)
@EPROM (Erasable PROM)
@EEPROM (Electrically Erasable PROM)
Secondary memory:
@The secondary memory is also called as the AUXILLARY
MEMORY
@It may be in-built or may be introduced into the computer and is

24. used to store the data on a PERMANENT basis
@The various types of secondary memory include:
Magnetic storage device:
@Use magnetism property to store data
@The data stored in these devices can be stored, erased,
rewritten many number of times
@Examples include: Magnetic tapes, magnetic disks, floppy disk,
etc
Optical storage device:
@Uses the LASER BEAMS to store data
@The data stored in these devices can be erased and rewritten
many number of times
@Examples include: CD, CD-ROM-CD-RW, DVD, etc.
Magneto-Optical storage device:
@This uses both MAGNETISM and LASER BEAMS to store data
@These devices are generally used in the cases of BACKUP, DATA
RECOVERY, etc,
@The data stored in the can be erased and rewritten many times

25. CU (CONTROL UNIT) ALU (ARITHMETIC LOGICAL UNIT)
Universal Serial Bus (USB):
@These are commonly called as pen drives
@These are compact and store large data than the other storage
devices
@These are connected to the USB PORT in the CPU
Central processing unit:
The CPU is the main functional unit of the computer. The basic
functions of CPU include:
@fetch the data from the user
@Decode the data into a computer-understandable form
@Process the data or execute the operation
@Store the result
This sequence of functions is called the INSTRUCTION CYCLE and is
represented as:

26. MAIN MEMORY
EXECUTE
FETCH
The various units of the CPU include:
ARITHMETIC LOGICAL UNIT (ALU):
@It is used to perform the various arithmetic and logical
operations.
@Arithmetic operations like +,-,*, / are performed by ALU
@Logical operations like >, <, =, =/= are performed by the ALU
with the help of logical gates like NOT, OR, AND, etc.
@The three basic concepts of the ALU include:
@Opcodes: The data on which the operation is to be executed
@Operands: The operations to be performed on the data
@Format code: The format in which the data is represented, For

27. example like, STATIONARY POINT OR FLOATING Pointed, etc
CONTROL UNIT (CU):
@The CU control the flow of information
@It is called THE BRAIN OF THE CPU
@It directs the tasks performed by the ALU and also the
functions carried out by the I/O DEVICES
REGISTERS:
@The CPU contains certain temporary storage units called as the
REGISRES.
@The various types of registers and their functions are:
@Program Counter (PC): Stores the next operation to be performed
@Information Counter(IC): Store the information or data to be
processed by the CPU
@Memory Address Register (MAR): Stores the address of the next
location in the memory
@Memory Buffer Register: Stores the data received from or sent
to the CPU
@Memory Data Register (MDR): Stores Operands and Data
Output units:

28. @These are electronic or electromechanical devices which give the
desired result or output to the user in the USER-
UNDERSTANDABLE format.
@The various output units include:
*Visual Display Unit (VDU) or Monitor
*Printer
*Computer Output Micro file
*Plotter
Monitor:
@The monitor is a visual display unit used to display the output to
the user and is often referred to as the ELECTRONIC MEDIA
Principle:-When the beams of electrons in the electrical signals
strike the inner side of the monitor containing RED, BLUE and
GREEN PHOSPHOROUS, the color and detail of the object is
visible depending on the PROPORTIONS OF THE COLOR and the
INTENSITY OF THE ELECTRON BEAMS
@The types of monitor include: Cathode Ray Tube (CRT) and Liquid
Crystal Display (LCD)
@Cathode ray is better at picture perception when compared to
LCD

29. @The CRITICAL PARAMETERS of the monitor include:
*SIZE (length, breadth, thickness)
*RESOLUTIONS (pixels)
@Video card is to be installed for better graphical perception
Printer:
@printer is used to get a printed or PHOTOCOPY of the document
or image present in the system.
@The types of printers include:
@DOTMATRIX PRINTERS: High speed printers but the quality of
the image is poor
@INKJET PRINTERS: Slower than the Dot-Matrix printers but
have good picture quality
@LASER PRINTERS: Since these printers have their own ROM,
RAM and MICROPROCESSOR and hence produce HIGH QUALITY
IMAGES WITH GOOD SPEED.
Quality of printers is measured using the CRITICAL PARAMETERS:
*DOT PER INCHES (DPI)
*PAGES PER MINUTE (PPM)
Speaker:
@It is an electromechanical device that converts ELECTRICAL

30. SIGNALS into SOUND WAVES
@AUDIO DEVICE DRIVER has to be installed for the speaker to
perform
@Speaker may be in-built or it may be separately attached to the
computer
@Quality of the speaker is dependent on the SOUND CARD
installed in the computer
@Sophisticated Speakers contain SUB-WOOFER SYSTEM to
increase the BASS OUTPUT
5. MEMORY UNIT OF THE COMPUTER AND VARIOUS TYPES OF
MEMORY (REFER MEMORY UNIT IN THE ORGANISATION OF
COMPUTERS)
6. EVOLUTION OF COMPUTERS:
• In earlier years, people used fingers, stones, pebbles, and
notches in sticks and knots in ropes to perform simple
arithmetic calculations.
• SAND TABLE:(EARLIER PERIOD)
 Used stones for calculations
 It contains three channels filled with sand and each
chamber can hold a maximum of 10 stones
• ABACUS:(2500 BC)
 It was invented by ASIA MINOR in 2500 BC.

31.  It consisted of a wooden frame with strings and
beads which were used for calculations.
• NAPIER’S BONE:(1614)
 This is a complicated manual device calculated by
JOHN NAPIER in 1614
 This device consisted of a board with nine rods
 The rod on the left corner consisted of digits from 1
to 9
 The rod at the extreme right consisted of ZEROS
and was called the CONSTANT ROD
 It was exclusively used for multiplying or dividing two
numbers only if one of the numbers is a single digit
• SLIDE RULE:(1620)
 It was devised by EDMUND GUNTER in 1620
 It consisted of two graduated scales sliding over
each other
 It was used to perform not only simple arithmetics,
but also complex calculations like LOGARITHM and
TRIGNOMETRIC ROOTS, etc.
• PASCALINE:(1642)
 It was devised by BLAISE PASCAL in 1642
 It was also called as the ROTATING WHEEL
CALCULATOR or NUMERICAL WHEEL CALCULATOR
 It was designed to handle numbers up to
999,999.999
• STEPPED RECKONER:(1694)
 Pascaline was improved by a German mathematician,
GOTFRIED WILHELM VON LEIBNIZ into a stepped
reckoner
 It performs multiplication, division and also SQUARE
ROOT of a number
• DIFFERENCE ENGINE:(1822)
 It was devised by CHARLES BABBAGE in 1882

32.  It used the features of the modern digital
computers like
INPUT,OUTPUT,STORAGE,PROCESSOR and
CONTROL UNITS
 It was designed to perform mathematical
calculations by getting two inputs from the user(a)a
set of programs that contains the instructions to be
executed(b)a list of variables on which the operation
is to be performed
 It was a digital automatic programmable general
purpose computer
 Its disadvantage was that it was a slow engine
taking 3 minutes to multiply 2 numbers of 20 digits
each
• 1883-The idea of analytical difference engine was given by
CHARLES BABBAGE
• 1889-The idea of punched cards as input was introduced by
HERMAN HOLERITH
• MARK-I(1994):
 It was devised by Aiken,an American mathematician
in 1937 and completed in 1994
 It is faster than difference engine. For example, it
can multiply two digits of 20 digits each within 6
seconds
 But it was slow in processing the results(RATE OF
RESULT=ONE RESULT/SECOND)
 It was noisy and large in size
• COLOSSUS(1994):
 It was devised by ALAN MATHINSON, a British
mathematician in 1994
 It was a pure electronic digital programmable
computer
 It used VACUUM TUBE TECHNOLOGY

33.  It was designed to perform only specific operations
• ENIAC(1946):
 Electronic Numerical Integrator And Calculator
developed by John Eckert and John Mauchley in
1946
 Used Vacuum tube technology for basic circuits
 Consisted of 17468 vacuum tubes, 7200 crystal
diodes, 10000 capacitors, 1000 relays
 1000 times faster than MARK-I
 Perform simple arithmetic and advanced operations
 Used DECIMAL SYSTEM for representing and
processing values
• EDVAC(1949):
 Electronic Discrete Variable Automatic Computer
devised by Eckert and Mauchley in 1949
 Worked on the principles of STORED
PROGRAMS(program and data are considered as
strings of BINARY DIGITS)
 Units are: Magnetic tape, Control unit, Dispatcher
unit, Processor, Timer, Dual memory, Three
temporary tanks to hold a single word
• EDSAC(1949):
 Electrical Delay Storage Automatic Calculator
developed by Maurice Wilkes in 1949
 Vacuum tube technology used for basic circuits and
MERCURY DELAY LINES for memory construction
 Input unit- Punched cards
 Output unit- Teleprinter
 Able to carry out 650 instructions per second
• UNIVAC(1951):
 Universal Automatic Computer developed by
ECKERT-MAUCHLEY corporation in 1951
 5200 Vacuum tubes were used for basic logic

34. circuits and MERCURY DATA LINES for memory
construction
 It can process numbers and alphabets
 Since it provided separate processors for handling
input, output and processing units, it was UNIQUE
among the early computers