The document defines what a computer is and provides details about how it works. It can be summarized as: 1) A computer is a device that processes data according to instructions to convert it into information. It works through an input-processing-storage-output cycle. 2) Computers are popular due to their speed, large storage capacity, reliability, and adaptability. They are now used in many fields. 3) Computer hardware includes input devices, a processing unit, storage devices, and output devices. The processing unit contains a control unit, arithmetic logic unit, and memory unit and uses a fetch-decode-execute-store machine cycle.

1. What is Computer?
The word computer is derived from a word compute which means “To calculate”. So simply we can say.
“Computer is a calculation device”
In another definition we can say.
“Computer is a device that converts data into information according to given instructions.”
Working of computer:
Computer convert data into information using a 4-steps process called IPC (Information Process Cycle).In
IPC.
1st
Step Data will be given in computer (input stage).
2nd
Step Computer will process that data to generate useful information (processing stage).
3rd
Step Computer will store the result (Storage stage).
4th
Step Computer will displayed result (Output stage).
For example if you want result of 2+2 by computer then IPC work as;
Input stage 2+2 will given in computer
Processing stage 2+2=4 the result will be calculated
Storage stage 4 will be store in computer
Output stage 4 will be displayed on screen
Here what is meant by Data & Information?
Data. Individual or raw facts about any things called Data”. e.g Ali ,50,RS etc
Information, Data after processing to give a useful and complete meaning is called Information.
Here question is that why this device is being too much popular? This is due to following reason.
Characteristics of Computer:
1: Speed Computer is speedy device. A problem that a man can solve in hours, can e solved by
computer in mill & micro seconds.
2: Storage Capacity. Computer is used due to its large storage capacity. A data that you can place in
100 (7*4) feet cupboard can be stored in a computer on a 2*2 inch area.

2. 3: Reliability. Computer is too much reliable it not gives wrong result and never tired if you use it
continuously. So it is accurate and tireless machine.
4: Adoptability Computer has ability to work with and to control each and every electronic device. You
can plug camera motors fax and many other machines with it to get required result.
Use of computer:
Due to above characteristics computer is being used in each and every field of life. Computer is working
is being used in households, Robotics, Technology, Offices, Industries, Banks, Railway, Airlines, Hotels to
keep record, Universities for research, in data communication and Telecommunication, for online
reservation, online shopping and online banking etc.
History:
There are many devices which were used to aid computation for thousands of years. Humans learned to
count on their hands. The abacus is first computing device in the human history used for arithmetic
tasks (Calculation). The Roman abacus was used in Babylonia as early as 2400BC.
A number of astronomical calculators were constructed in ancient and medieval times. There are many
inventions made by Abu Rayhan al Beyruni (AD 1000).
Al-khuwarzini is derived basic concept known is Algorithms, while bee basic for the modern
computation. John Napier (1550-1617) designed Napier’s bones, an abacus-like device used for
multiplication and division. In 1890, the united stats Census Bureau used punched cards, sorting
machines, and tabulation machines designed by Herman Hollerith to handle.
In early days of 1940, Scientist develop machine naming ENIAC, EDVAC that were using vacuum tubes.
After 1959 by development in electronics, semi conductors, diodes come on screen. Computer
manufacturing companies like IBM use this new technology and make machine like UNIVAC, CDC1604.
In third generation machine integrated circuits (IC) were used. That was 1965 when multiprocessing
concept introduced. In 1981 IBM released first personal computer (PC). The computer is now being used
in each and every field of life not only for calculation but also for controlling other machines and to
perform other logical operations.
In 1990 Microsoft released window 3.0 that make computer more favorite and easy to use tools. After
1990, there was a great revolution in computer hardware as well as a software field. Concept of large
scale integration and very large scale integration introduced in hardware side, plug and play and hot
boot future introduced on software side. After 2000 Database management system and artificial
intelligence introduced.

3. Types of Computers:
1: Super Computer:
These are largest in size, fast in speed & have a capacity to perform many people tasks. More than 1000
people can work at a time in single super computer. Speed of this computer is measured in BIPS (Billion
Instruction per Second). A instruction mean statement to perform a task. So, in on second these
computers can execute one billion instructions. These computers are being used in Aerospace
Technology & Atomic energy.
2: Mainframe computer:
These are second category computers. These are smaller than super computer but these are also large
computer, fast in speed but slow as compared to super computer. On such type of computer 100 to
1000 people can work at a time. Speed of these computer is measured in be processed in one second.
These computer are being use in large organization as by Air force, Navy, Pakistan steel mills large Bank
& and agha khan University is also using such computers.
3: Mini Computer:
These are 3rd
category computers. These are small in size with low speed aw compared to super &
Mainframe computer. On such types of computer up to 500 people can work at a time. Speed of these
computer is measured in KIPS (Kilo Instruction per Second). These computers are being used in middle
size companies & organizations like hotel, railways, PIA & super store etc.
4: Micro or Personal Computer
These are the smallest type of computer being used these days. These have slow speed as compared to
super, mainframe & mini computers, just one man can work on such types of computer the price is so
less that a person can purchase it. So, it is also called PC (personal Computer). Speed of this computer is
measured in Hz, GHz, and MHz it is being used in small officers, home for calculation & entertainment.
Computer Hardware & Software and input Devices
Computer is collection of two basic components i.e Hardware and software.
Hardware:
Hardware is known as physical parts of computer. All the tangible (which one can touch and see) devices
such as key board, mouse, monitor, CPU, etc.
Software:
Software is a set of instructions given to computer for performing any specific tasks. These are programs
that order hardware to do specific work. For example typing tutor, window, MS word, etc.

4. Type of Hardware’s
We divided computer hardware in further 4 groups.
1. Input Devices
2. Processing Unit
3. Storage Devices
4. Output Devices.
1: Input Devices:
Input means giving data in computer. Input devices are devices used to input data. Some input devices
are keyboard, Mouse, Digital Camera, Scanner etc.
Central Processing Unit
Data after given in computer is processed by a device called CPU (Central Processing Unit) or processor.
The work done by processor on data is called processing. Processing include calculation, rearrangement
of data, conversion of data from one format to another and to control all other hardware and software
of computer. Keep in mind that computer is an electric device and manipulate all data internally in form
of 0 & 1 also called binary code.CPU is brain of computer and is responsible for all tasks in computer.
Part of CPU:
The CPU consists on 3 parts they are CU, ALU, and MU.
CU: CU stand for control unit. It controls all hardware and software of computer. It is also
responsible to convert all data into 0 & 1.
ALU: ALU stand for arithmetic and logical unit. It performs all arithmetic (+, -, *, /) comparison (<,>, =)
and logical operation all AND, NOR, ETC) in computer.
MU: MU stands for memory unit. It consists on small storage place called registers. Data store in this
unit for a moment.
Machine Cycle: Processor process all data using a cycle called machine cycle. It is a 4 step cycle with.
Step- 1: Fetch. To take data from MU to CU.
Step- 2: Decode To convert data in 0 and 1.
Step- 3: Execute To solve arithmetic and logical operation.
Step-4: Store: To save processed data in MU.
Processor speed:

5. The speed by which a computer can process a command complete a task or work is known as processing
speed. In early days this speed was measured in seconds mile seconds and micro seconds. But with
development in electronics speed goes behind to be measured in seconds and now a day it is being
measured in hertz.
Units to Measure processor speed:
Hertz (HZ). Number of cycles per second is called Hertz other big units to measure processor speed are.
1024 Hertz = 1 kilo Hertz (1 KHz)
1024 Kilo Hertz = 1 Mega Hertz (1 MHz)
1024 Mega Hertz = 1 Gega Hertz (1 GHz)
Speed of Micro computer /PC’s processor measured in GHz. And Mini, Mainframe, and Super
computer’s processor speed is measured in instructions per second (IPS).
Storage Devices:
After processing of data next step is to store data. For storing data in computer we use storage device
such as Magnetic Tap, Hard disk, CD Flash Memory.
Units to Measure Storage Devices:
Bit: A bit is a binary digit, taking a value of either 0 or 1. For example, the number 10010111 is 8 bit long
number. Binary digits are a basic unit of information storage and communication in digital computing
and digital information theory.
4 bit from 1 Nibble
8 bit from 1Byte
1024 bytes from 1 kilobyte (KB)
1024 KB from 1 megabyte (MB)
1024 MB from 1 gegabyte (GB)
The bit is a unit of measurement, the information capacity of one binary digit. It has the symbol bit.
Type of storage Devices:
Storage devices are grouped in two categories.
1: primary Storage Devices
2: Secondary Storage Devices