This document provides an overview of computers. It discusses what a computer is, its main components including the input unit, CPU, output unit, and memory. It describes how the arithmetic logical unit and control unit function. It also covers computer hardware, software, operating systems, and the evolution of computers from early counting devices like the abacus to modern computers. It classifies computers according to their purpose, use, and technology.

1. *COMPUTEROVERVIEW*
* MADE
BY:ULTRON

2. *INTRODUCTION*
• Computers have made great inroads in our everyday life and
thinking.They areput to use for all sorts of applications
ranging from complex calculationin the fieldor frontline
research, engineeringsimulationdown to teaching,printing
books and recreational games . The ease with which
computers can process data, store and retrieve it painlessly
have made them inevitablein office andbusiness
environments. The area of application of computers are
confirmed only by limitationon humanscreativityand
imagination.

3. *WHATISACOMPUTER?

 It canstore data and information in its memory ,
process them and producethe desiredresult .
 It is used essentiallyas a data processor. theterms data
and informationare very commonly used.

6. *FUNCTIONALCOMPONENTSOFACOMPUTER:
1. INPUT UNIT
2. CPU
3. OUTPUTUNIT
4. MEMORY

7. * INPUT UNIT *

9. *ARITHMETICALLOGICALUNIT(ALU)*
*THE ALU PERFORMSALL THE FOUR ARITHMETICAL (+,-,*,/)
AND SOME LOGICAL(<,>,=,<=,>=)OPERATIONS.
*WHENTWO NUMBERSARE REQUIREDTO BE ADDED,THESE
NUMBERSARE SENTFROMMEMORYTO ALU WHERETHE
ADDITION TAKES PLACE AND THE RESULT IS SENT BACKIN
THE MEMORY.ANDTHE SAME FOR LOGICAL
OPERATIONS.AND THE RESULTS FOR THE LOGICAL
OPERATIONS IS EITHERTRUE OR FALSE

10. *CONTROLUNIT(CU)*
* CU ACTS AS A SUPERVISOR BY CONTROLLING AND
GUIDING THE OPERATIONS TAKING PLACES .
* THE CU SENDS THE CONTROL SIGNAL UNTIL THE
REQUIRED OPERATION ARE DONE PROPERLY BYALU.
* CU CARRYING OUT ALL THE INSTRUCTIONS
STORED IN THE PROGRAMS

11. *OUTPUTUNIT*
* OUTPUT UNIT CONVERTS THE OUTPUT IN BINARY
FORMTOHUMAN REDABLE FORM.
* THE OUTPUT UNIT IS FORMED BYTHE OUTPUT
DEVICES ATTACHED TO THE COMPUTER.
* SOME POPULAR OUTPUT DEVICES ARE:-
VDU(VISUAL DISPLAY UNIT),PRINTER,PLOTTER AND
CODDER ETC.

12. *THEMEMORY OFTHE COMPUTERIS OFTENCALLEDMAIN
MEMORY.IT ISGENERALYTHIRD COMPONENTOF CPU.
* THEMEMORY OFTHECOMPUTERIS THOUGHT OFAS THE
‘CELLS’.EACHOF THESECELLSIS FURTHERBROKEN DOWN INTO
THE SMALLERPARTSKNOWN AS BITS.
*A BITMEANSA BINARYDIGIT i.e.either0 or 1.A NUMBEROF BITS
TOGETHER AREUSED TO STOREDATAINSTRUCTIONBY THEIR
COMBINATION.
*ONE BYTE IS THE SMALLESTUNITWHICHCANREPRESENTA DATA
ITEMOR A CHARACTER.OTHERUNITSAREKB,MB,GB,TB.
*THEMEMORY*

13. *BITS&BYTES*
* Each of these memory cells is further broken down into smaller
parts known as bits. A bit means a binary digit i.e. either 0 or 1. A
number of bits together are used to store data instructions by
their combinations.
*A bit is an elementaryunitof memory.
* A group of 8 bits is called a byte and a group of 4 bits is called a
nibble.
* One byte is the smallest unit which can represent a data item or
a character.

15. *PRIMARYANDSECONDARYMEMORY*
* PRIMARY MEMORY:-ITS IS USED FOR STORING
TEMPORARILY
* THEY ARE OF TWO TYPES:-
1. RAM(RANDOM ACESS MEMORY)
2. ROM(READ ONLY MEMORY)
* SECONDARY DATA :- IT IS USED FOR STORE DATA
PERMANENTLY

16. *HARDWARE *
* HARDWARE :- Hardwarerepresentthe physicaland
tangible components of the computer i.e,the
components that can be touched andseen .
“Examples ” :-CPU ,floppy disk, hard disk etc.
* PERIPHERAL :- Peripheralare the devicesthat
surroundthe system unit .
“ Example”:- keyboard,mouse,speaker,printer
,monitors ,etc.

17. * Software represent the set of programthat governs
the operations of a computer systemand make the
hardware run.
* Software classified in three forms:-
1. Operating system
2. Language processors
3. Applications software

18. OS(INTERFACE MANAGER)
* AN OPERATING SYSTEMIS A PROGRAM WHICH
ACTS AS AN INTERFACE BETWEEN THE USER AND
THE HARDWARE(i.e, ALL THE COMPUTER
RESOURCES) AND CONTROL ALL OTHER
COMPONENTS OF THE COMPUTER SYSTEM.
user
Application
software
Operating
system
CPU and
hardware

19. *TYPESOFOS*
*THEREARE VARIOUS TYPES OF OS :- Singleuser
OS,multiuserOS, batch processing OS,multiprocessingOS,
etc.
*AS THE NAME SUGGESTSingleuser OS SUPPROT SINGLE
USER, MultiuserOS SUPPORTS MULTIPLEUSER. THE batch
processing OS PROCESSES THE BATCH (GROUP)OFJOBS
(PROCESS GIVENTO IT) AND MultipleprocessingOS IS
CAPABLE OF HANDLING MULTIPLE CPU AT THE SAME
TIME.

20. * IT PROVIDE THE INSTRUCTION TO PREPARE USER-INTERFACE i.e,
WAY TO INTERACT WITH USER WHETHER THROUGH TYPED
COMMANDS OR THROUGH GRAPHICALSYMBOLS.
* IT LOADSNECESSARY PROGRAMS (INTO THE COMPUTER
MEMORY) WHICH ARE REQUIRED FOR A PROPER COMPUTER
FUNCTIONING.
* IT COORDINATES HOW THE PROGRAMWORKS WITH THE
CPU,KEYBOARD, MOUSE, PRINTERANDOTHER HARDWAREAS WELL
AS WITH OTHER SOFTWARE.
* IT MANAGES THE WAY INFORMATION IS STORED ON AND
RETRIEVED FROM DISKS.

21. *LANGUAGEPROCESSOR*
* THESE TRANSLATETHE USER ORIENTED LANGUAGE INTO
MACHINELANGUAGE.
* THESE ARE OFTHREE TYPES:-
1. ASSEMBLER :- THESE TRANSFERASSEMBLY LANGUAGE INTO
MACHINELANGUAGE.
2. INTERPRETER :- THESE TRANSLATE HLL(HIGHLEVEL LANGUAGE
INTO MACHINELANGUAGE(ML)LINE BY LINE . IF THERE IS ANY
ERROR,IT REPORTS AT THE SAME TIME.
3. COMPILER :- THESE TRANSLATE HLL(HIGHLEVEL LANGUAGE )
INTO MACHINELANGUAGE IN ONE GO & REPORT ALLERROR
ALONGWITH THE LINE NUMBER

22. *COMPILER*
* Compiler : It also converts a HLL program into
machine language but a manner which is way
different from a n assembler. It converts the
entire program in one go, and reports the errors
ofthe programalong with linenumbers.
* A combination of compiler and assembler is
best upto therequirement. .

23. *APPLICATIONSOFTWARE*

24. *STRENGTHOFCOMPUTER*
1. Its speedis much faster as comparedto human beings.
2. It has high storage capacity.
3. It can performall the calculations andcomparisons
accurately.
4. Computers are more reliable than human beings.
5. Computers are versatile to repetitive jobs.

25. *WHATITLACKS*
* But the advantages counted limitations remain
because limitations must followadvantages.
*Here limitations are :-
1. LACK OF DECISION MAKING POWER. Computers
cannot decideon their own. They lackthe powerwhich
is a greatasset to us and everybody who is a human.
2. IQ ZERO. Computers are dumb machineswith zero
IQ. They need to be told

26. *FIRMWARE&LIVEWARE*
* Firmware is a pre-written program that is
permanently stored in read-only memory. It
configures the computer and is not so easily
modifiable by the user. BIOS (Basic Input and
Output services) instructions are an example of
firmware.
* It is the term generally used for the people
associated with and benefited from the computer
system.

27. *EVOLUTIONOFCOMPUTERS*
* Ancient people used stones for counting or
made scratches on wall or tied knots in a rope to
record information. But all these were manual
computing techniques. Attempts had been going
on for developing faster computing devices and
the first achievement was abacus, the pioneer
computing device used by man.

28. *ABACUS*
* Around 3000 B.C, the Mesopotamians quite
unknowingly laid the foundation of computer era.
* They discovered an earliest form of a bead-and-
wire counting machine, which subsequently came
to be known as abacus. The Chinese improved upon
the abacus so that they could calculate and count
faster.

29. *NAPIER’S‘LOGS’AND‘BONES’*
* John napier (1550-1617) developed the idea of
logarithm. He used logs to transform multiplication
problem to addition problem. Napier’s logs and bones
later became basis for a well known invention known –
the computing machine known as “slide rule” (invented
in 1662). Napier also advised a set of numbering rods
known as Napier's bones. He could perform both
multiplicationand division with these ‘bones’.

30. *PASCAL’SADDINGMACHINE*
* The idea of logarithm, developed in 1614,
notably reduced the tedium of repetitive
calculations.
* Blasé Pascal, a French mathematician, invented a
machine in 1642 made up of gears which was used
for adding numbers quickly. This machine was
known as adding machine (also known as
Pascaline) and was capable of addition and
subtraction.

31. *PASCALINE*
* It worked on clock work mechanism
principle. The adding machine consisted of
numbered toothed wheels having unique
position values. The rotation of wheels
controlled the addition and subtraction
operations. The machine was capable of
carry-transferautomatically.

32. *LEIBNITZ’SCALCULATOR*
* Gottfried Leibnitz, a german mathematician,
improved an adding machine and constructed a
new machine in 1617 that was capable to perform
multiplication and division as well. This machine
performed multiplication through repeated
addition of numbers. Leibnitz’s machine used
stepped cylinder each with nine teeth of varying
lengths instead ofwheels as was used by Pascal.

33. *JACQUARD’SLOOM*
* Joseph jacquard manufactured punched cards at
the end of American revolution and used them to
control looms in 1801. Thus the entire control of
weaving process was automatic. The entire
operation was under control of a program . with
the historic invention of punched cards, the era of
storing and retrieving information started that
greatly influenced the later inventions and
advancements.

34. *BABBAGE’SDIFFERENCEENGINE*
* Charles Babbage, a professor of mathematics,
developed a machine called DIFFERENCE ENGINE in
the year 1822.this machine was expected to calculate
logarithmic table to a high degree of precision. The
difference engine was to calculate various
mathematical functions. The machine was capable of
polynomial valuation by finite difference and it’s
operation was automatic Multi-stop operation.

35. *BABBAGE’SANALYTICALENGINE*
* In 1833, Charles Babbage started
designing an analytical engine which was
to become real ancestor of modern day
computer. With the methodical design of
his analytical engine, babbage
meticulously established the basic
principles on which today’s computers
work.

36. * The first innovation enabled the machine to
compare quantities and then decide which of the
instruction sequences to follow. The second
permitted the results of a calculation to change
numbers and instructions already stored in the
machine.
* His great inventions of difference engine and
analytical engine earned Charles Babbage the
title “FATHER OFMODERNCOMPUTERS”.

37. *MARK-1*
* Prof. Howard Aiken (1900-1973) in USA
constructed in 1943 an electromechanical computer
called mark-1 which could multiply two ten digit
numbers in 5 seconds- a record back then.MARK-1
was the first computer which could perform
automatically without any manual intervention
accordingto preprogrammed codes.

38. *THEGENERATIONSOFMODERNCOMPUTERS*
* The term ‘computer generation’ is
often used in connection with computer
hardware.
* These are in fact phases of
development characterized by type of
switching circuit it utilizes.

39. *STOREDPROGRAMCOMPUTER*
* Most computers today use the idea of ‘stored program
computer’proposed by Dr.johnvonNeumannin1945.
* The 3 key conceptofthe architectureare:-
1. Data and programs are stored in a single read-write
memory.
2. Thememorycontentsareaddressablebylocations.
3. Execution takes place in a sequential fashion i.e.
from one instruction to the next unless modified
explicitly.

40. *Thegenerationofmoderncomputer*
*There are fivetypes of generations:-
1. The First generation computer (1949-55)
2. The Secondgeneration computer(1956-65)
3. The Third generation computer(1966-75)
4. The Fourth generation computer (1976-
present)
5. The fifth generation computer

41. *Keyfeatureof Firstgenerationcomputer(1949-55)*
* Usedvacuumtubes.
* Big clumsycomputers.
* Highelectricity consumption.
* Electric failure occurred regularly-computernot very reliable.
* Largeair conditioner were necessarybecause the computer
generated heat .
* Programmingin ML(machinelanguage).

42. *KeyfeaturesSecondgenerationcomputer(1956-65)*
*Transistorreplaced vacuumtubes.
*Smallercompared tofirst generation.
*Generated less heat.
*Lower electricity consumption
*More reliable and faster
*Core memory developed
*Magnetic tapes anddisksused
*Firstoperating systemdeveloped
*Programmingin machinelanguage aswell asmachinelanguage.

43. *KeyfeatureofThirdgenerationcomputer(1966-75)*
*Integrated circuitsare
used
*Computer smaller faster
and morereliable
*Lower power
consumption.
*High-level language
appeared.

44. *KeyfeaturesofTheFourthgenerationcomputer(1976-present)*
* Integratedcircuit,smallerand faster.
* Microcomputerseriessuch as IBM and APPLE
developed
* Portable computerdeveloped
* Great development in data communication
* Different types of computermemory with high
storagecapacity
* Fast accessdeveloped.

45. *Keyfeatureof Thefifthgenerationcomputer*
* PARALLEL-PROCESSING - Many processorsare
groupedto function as one largegroup processor.
* SUPERCONDUCTORS - A super conductoris a
conductor through which electricitycan travel
without any resistanceresulting in faster transfer
of information between the components of a
computer

46. *CLASSIFICATIONSOFCOMPUTERS*
*Computers can be classified into different
categories depending upon following
criteria:
1. According to Purpose.
2. According to Use.
3. According to Technology Used.
4. According to Size and Storage Capacity.

47. *ClassificationAccordingtopurpose*
1. Specialpurpose computers:It is a computerused to
performa specifictask only. In this type of computer,
instructions are permanentlystored. Forexample,
computer used for weatherforecasting.
2. Generalpurpose computers: It is a computer used to
performvariety of applications.Instructionsare
loaded at the time of need andarenot permanently
stored.For example, computer used to perform
various calculations.

48. *ClassificationAccordingtoUse*
1. Scientific Computers: These computers have
slow input/output devices but have fast
processing speed. So these are quite suitable for
scientific applications.
2. Business Computers: These have fast
input/output devices but slow processing speed.
So these are quite suitablefor business
applications.

49. * ClassificationAccordingtoTechnologyused*
1. Digital Computers: They convert data into
binary digits (0 or 1) and then process them.
2. Analog Computers: They work on physical
quantities.
3. Hybrid Computers: They are the mixture of
Digital and Analog computers.