This document provides an overview of the basic components and operations of a computer system. It discusses how a computer system is composed of input, output, processing, memory, and controlling units. The central processing unit (CPU) acts as the brain and contains the arithmetic logic unit (ALU) and control unit to process data. Memory, including primary memory like RAM and ROM, is used to store programs and data both temporarily for processing and more permanently. Input and output devices allow the user to interface with the computer system by entering and receiving data. The five basic operations of a computer system are inputting, storing, processing, outputting, and controlling data.

1. BASIC OF
OPERATING
SYSTEM

2. ORGANIZATION OF A
COMPUTER SYSTEM
Definition:-
A computer system is an electronic device including all the
hardware and software required to make it functional for a
user.
It should have the ability to receive user input, process data,
and with the processed data, create information for storage
and/or output.
A computer consist of mainly three main components units
.These are Input/Output units,Central processing unit(CPU)
and Memory unit.

3. CONTINUED……….
All types of computer follow a same basic logical structure and
perform the following five basic operations for converting raw
input data into information useful their user:
The five basic operation are discussed below:
 Inputting
 Storing
 Processing
 Outputting
 Controlling

5. Input Device Output Device

6. INPUT DEVICES
This unit contains devices with the help of which we enter data into computer.
This unit makes link between user and computer.
Input devices are hardware components that enable users to interact with a
computer. Without input devices, you would not be able to feed instructions to a
computer. The most common input devices in computer is following
 Mouse
Joystick
Trackboll
Light pen
Graphic Tablet
Touch Screen
Microphone
OCR
OMR etc.

7. OUTPUT
DEVICE/UNITS
Output unit devices with the help of which we get the
information from the computer. This unit is a link computers
and users.
An output device is any peripheral that receives data from a
computer, usually for display, projection, or physical
reproduction. For example, the image shows an inkjet printer,
an output device that can make a hard copy of any
information shown on your monitor, which is another
example of an output device.

8. CENTRAL PROCESSING
UNIT(CPU)
 The central processing unit is a brain of any system.In computer all
major calculations, manipulations and comparisons made by CPU.
 A computer's CPU handles all instructions it receives
from hardware and software running on the computer.
 The primary function of a Central Processing Unit is to execute
instruction or programs.
 The major parts of a Central Processing Unit(CPU) are:
a) Primary or Main Memory
b) Arithmetic and logic unit(ALU)
c) Control Unit

9. PRIMARY MEMORY
Primary memory or main memory is a one of a major part of a
computer. It is also known as internal memory or RAM.
Primary memory is use to store information in memory. The
main memory stores programs along with data , which are to
be executed
It allows a processor to access running execution applications
and services that are temporarily stored in a specific memory
location.
Primary memory is the area in a computer in which data is stored
for quick access by the computer's processor.

10. ARITHMETIC LOGIC
UNIT
ALU of a computer system is the place where the actual
execution of instructions takes place. All calculations are
performed and all comparisons(decisions) are made in ALU.
An ALU can be designed by engineers to calculate any operation.
As the operations become more complex, the ALU also becomes
more expensive, takes up more space in the CPU and dissipates
more heat.
ALU performs basic arithmetic(add,substract,multiply,divide) and
logical operation(Greater than,lesser thanor equal to)

11. CONTROL UNIT
A control unit (CU) (or controller, same thing) is a piece
of hardware that manages the activities of peripherals (separate
devices attached to the computer, such as monitors, hard
drives, printers, etc.)
In other words control unit is work like a controller that is control
all process and hardware device and instruct to all for their work
and define their jobs.
The control unit fetches one or more new instructions from
memory (or an instruction cache), decodes them and dispatches
them to the appropriate functionalunits

13. MEMORY
• A computer needs to store data. It also needs memory to
perform arithmetical operations and storing programs and
pictures. Computer memory is of two types:
A. Primary Memory
B. Secondary memory

14. PRIMARY MEMORY
Primary memory is a part of the CPU whereas the secondary
memory is external to the CPU. When the electricity to the PC
is cut off the primary memory looses all the data immediately.
Primary memory is made up of electronic circuits and keeps
data as long as voltage supply is on. When power supply to a
PC is switched off, the data is lost.
Primary memory can be divided into the following two types:
a) RAM(Random access memory)
b) ROM(read only memory)

15. RAM
RAM stand for Random Access Memory. It performs both read
and write operations on memory. If power failures happened in
systems during memory access then you will lose your data
permanently. So, RAM is volatile memory. RAMs of various
capacities are available, for example ,512MB,4GB and 8GB
RAMs are available for PCs.

16. STATIC AND DYNAMIC
RAM
1. SRAM is static while DRAM is dynamic
2. SRAM is faster compared to DRAM
3. SRAM consumes less power than DRAM
4. SRAM uses more transistors per bit of memory compared to
DRAM
5. SRAM is more expensive than DRAM
6. Cheaper DRAM is used in main memory while SRAM is
commonly used in cache memory