A computer is an electronic device, operating under the control of instructions stored in its own memory that can accept data (input), process the data according to specified rules, provide information (output), and store the information for future use

1. Introduction to Computer System
Prepared By:
Sweta Kumari Barnwal
Assistant Professor
Arka Jain University

2. Introduction
Computer: A computer is an electronic device, operating under the control of
instructions stored in its own memory that can accept data (input), process the data
according to specified rules, produce information (output), and store the information
for future use1.
Functionalities of a computer
Any digital computer carries out five functions in gross terms:
 input function,
 process function,
 output function,
 storage function and
 Control over above functions
Processing
I/P O/P
Storage
Computer
System

3. Computer Components
Any kind of computers consists of HARDWARE & SOFTWARE.
Hardware: Computer hardware is the collection of physical elements that
constitutes a computer system. Computer hardware refers to the physical parts or
components of a computer such as the monitor, mouse, keyboard, computer data
storage, hard drive disk (HDD), system unit (graphic cards, sound cards, memory,
motherboard and chips), etc. all of which are physical objects that can be touched.
Software: Software is a generic term for organized collections of computer data
and instructions, often broken into two major categories: system software that
provides the basic non-task-specific functions of the computer, and application
software which is used by users to accomplish specific tasks.

4. Hardware
Input Devices
• Input device is any peripheral (piece of computer hardware equipment to provide
data and control signals to an information processing system such as a computer
or other information appliance.
• Input device Translate data from form that humans understand to one that the
computer can work with. Most common are keyboard and mouse.
Ex: Mouse, Keyboard, Scanner, Joystick, Stylus, Touchpad, Microphone, Digital
Camera, Barcode Reader etc.
Output devices
• An output device is any piece of computer hardware equipment used to
communicate the results of data processing carried out by an information
processing system (such as a computer) which converts the electronically
generated information into human-readable form.
Ex: Screen, Printer, Speaker, Plotters, Projectors etc.

5. Hardware
Central Processing Unit (CPU)
• A CPU is brain of a computer. It is responsible for all functions and processes.
Regarding computing power, the CPU is the most important element of a
computer system.
• The CPU is comprised of three main parts :
 Arithmetic Logic Unit (ALU): Executes all arithmetic and logical operations.
Arithmetic calculations like as addition, subtraction, multiplication and division.
Logical operation like compare numbers, letters, or special characters
 Control Unit (CU): controls and co-ordinates computer components.
• 1. Read the code for the next instruction to be executed.
• 2. Increment the program counter so it points to the next instruction.
• 3. Read whatever data the instruction requires from cells in memory.
• 4. Provide the necessary data to an ALU or register.
• 5. If the instruction requires an ALU or specialized hardware to complete,
instruct the hardware to perform the requested operation.
 Registers :Stores the data that is to be executed next, "very fast storage area".

6. Hardware
Primary Memory:-
• RAM: Random Access Memory (RAM) is a memory scheme within the
computer system responsible for storing data on a temporary basis, so that it can
be promptly accessed by the processor as and when needed. It is volatile in
nature, which means that data will be erased once supply to the storage device is
turned off. RAM stores data randomly and the processor accesses these data
randomly from the RAM storage. RAM is considered "random access" because
you can access any memory cell directly if you know the row and column that
intersect at that cell.
• ROM (Read Only Memory): ROM is a permanent form of storage. ROM stays
active regardless of whether power supply to it is turned on or off. ROM devices
do not allow data stored on them to be modified.

7. Hardware
Secondary Memory:-
• Stores data and programs permanently :its retained after the power is turned off
• 1. Hard drive (HD): A hard disk is part of a unit, often called a "disk drive,"
"hard drive," or "hard disk drive," that store and provides relatively quick access
to large amounts of data on an electromagnetically charged surface or set of
surfaces.
• 2. Optical Disk: an optical disc drive (ODD) is a disk drive that uses laser light
as part of the process of reading or writing data to or from optical discs. Some
drives can only read from discs, but recent drives are commonly both readers and
recorders, also called burners or writers. Compact discs, DVDs, and Blu-ray
discs are common types of optical media which can be read and recorded by
such drives. Optical drive is the generic name; drives are usually described as
"CD" "DVD", or "Bluray", followed by "drive", "writer", etc. There are three
main types of optical media: CD, DVD, and Blu-ray disc. CDs can store up to
700 megabytes (MB) of data and DVDs can store up to 8.4 GB of data. Blu-ray
discs, which are the newest type of optical media, can store up to 50 GB of data.
This storage capacity is a clear advantage over the floppy disk storage media (a
magnetic media), which only has a capacity of 1.44 MB.

8. Software
• System software is responsible for controlling, integrating, and managing the
individual hardware components of a computer system so that other software and
the users of the system see it as a functional unit without having to be concerned
with the low-level details such as transferring data from memory to disk, or
rendering text onto a display. Generally, system software consists of an operating
system and some fundamental utilities such as disk formatters, file managers,
display managers, text editors, user authentication (login) and management tools,
and networking and device control software.
• Application software is used to accomplish specific tasks other than just
running the computer system. Application software may consist of a single
program, such as an image viewer; a small collection of programs (often called a
software package) that work closely together to accomplish a task, such as a
spreadsheet or text processing system; a larger collection (often called a software
suite) of related but independent programs and packages that have a common
user interface or shared data format, such as Microsoft Office, which consists of
closely integrated word processor, spreadsheet, database, etc.; or a software
system, such as a database management system, which is a collection of
fundamental programs that may provide some service to a variety of other
independent applications.

9. Characteristics of Computer
Speed, accuracy, diligence, storage capability and versatility are some
of the key characteristics of a computer. A brief overview of these
characteristics are
• Speed: The computer can process data very fast, at the rate of millions
of instructions per second. Some calculations that would have taken
hours and days to complete otherwise, can be completed in a few seconds
using the computer. For example, calculation and generation of salary
slips of thousands of employees of an organization, weather forecasting
that requires analysis of a large amount of data related to temperature,
pressure and humidity of various places, etc.
• Accuracy: Computer provides a high degree of accuracy. For example,
the computer can accurately give the result of division of any two
numbers up to 10 decimal places.
• Diligence: When used for a longer period of time, the computer does
not get tired or fatigued. It can perform long and complex calculations
with the same speed and accuracy from the start till the end.

10. Characteristics of Computer
• Storage Capability: Large volumes of data and information can be stored in
the computer and also retrieved whenever required. A limited amount of data can
be stored, temporarily, in the primary memory. Secondary storage devices like
floppy disk and compact disk can store a large amount of data permanently.
• Versatility: Computer is versatile in nature. It can perform different types of
tasks with the same ease. At one moment you can use the computer to prepare a
letter document and in the next moment you may play music or print a
document. Computers have several limitations too. Computer can only perform
tasks that it has been programmed to do.

11. Classification of Computer
Sr. No. Type Specifications
1
PC (Personal
Computer)
It is a single user computer system having
moderately powerful microprocessor
2 Workstation
It is also a single user computer system,
similar to personal computer however has a
more powerful microprocessor.
3 Mini Computer
It is a multi-user computer system, capable of
supporting hundreds of users simultaneously.
4 Main Frame
It is a multi-user computer system, capable of
supporting hundreds of users simultaneously.
Software technology is different from
minicomputer.
5 Supercomputer
It is an extremely fast computer, which can
execute hundreds of millions of instructions
per second.

12. Personal Computer
• It can be defined as a small, relatively inexpensive computer designed for an
individual user. PCs are based on the microprocessor technology that enables
manufacturers to put an entire CPU on one chip. Businesses use personal
computers for word processing, accounting, desktop publishing, and for running
spreadsheet and database management applications. At home, the most popular
use for personal computers is playing games and surfing the Internet.
• Although personal computers are designed as single-user systems, these systems
are normally linked together to form a network. In terms of power, now-a-days
high-end models of the Macintosh and PC offer the same computing power and
graphics capability as low-end workstations by Sun Microsystems, Hewlett-
Packard, and Dell.

13. Workstation
• Workstation is a computer used for engineering applications (CAD/CAM),
desktop publishing, software development, and other such types of applications
which require a moderate amount of computing power and relatively high
quality graphics capabilities.
• Workstations generally come with a large, high-resolution graphics screen, large
amount of RAM, inbuilt network support, and a graphical user interface. Most
workstations also have mass storage device such as a disk drive, but a special
type of workstation, called diskless workstation, comes without a disk drive.
• Common operating systems for workstations are UNIX and Windows NT. Like
PC, workstations are also single-user computers like PC but are typically linked
together to form a local-area network, although they can also be used as stand-
alone systems.

14. Mini, Main & Super Computers
• Minicomputer is a midsize multi-processing system capable of supporting up to
250 users simultaneously.
• Mainframe is very large in size and is an expensive computer capable of
supporting hundreds or even thousands of users simultaneously. Mainframe
executes many programs concurrently and supports many simultaneous
execution of programs.
• Supercomputers are one of the fastest computers currently available.
Supercomputers are very expensive and are employed for specialized
applications that require immense amount of mathematical calculations (number
crunching). For example, weather forecasting, scientific simulations, (animated)
graphics, fluid dynamic calculations, nuclear energy research, electronic design,
and analysis of geological data (e.g. in petrochemical prospecting).

15. Generation of Computers
• Generation in computer terminology is a change in technology a computer is/was
being used. Initially, the generation term was used to distinguish between
varying hardware technologies. Nowadays, generation includes both hardware
and software, which together make up an entire computer system.
• There are five computer generations known till date. Each generation has been
discussed in detail along with their time period and characteristics.
– First Generation: (1946-1959) (Based on Vacuum Tubes) (Ex: ENIAC,
EDVAC, UNIVAC, IBM-701, IBM-650)
– Second Generation: (1959-1965) (Based on Transistors) (Ex: Honeywell
400, IBM 7094, CDC 1604, CDC 3600, UNIVAC 1108)
– Third Generation: (1965-1971) (Based on ICs) (Ex: PDP-8, PDP-11, ICL
2900, IBM 360, IBM 370)
– Fourth Generation: (1971-1980) (Based on Microprocessors) (Ex: IBM
4341, DEC 10, STAR 1000, PUP 11)
– Fifth Generation: (1980- till date) (Based on AI) (Ex: Desktop, Laptop,
NoteBook, UltraBook, Chromebook)