The document provides an overview of the basic organization of a computer, highlighting its three main components: the input unit, output unit, and central processing unit (CPU). It describes the functions of various units within the CPU, including the arithmetic and logical unit, memory unit, and control unit, along with details on main and auxiliary memory types. Key points include the characteristics of volatile (e.g., RAM) and non-volatile memory (e.g., ROM, auxiliary storage) and their roles in data processing.

1. General Computer
By
Dr. I. Uma Maheswari
Iuma_Maheswari@yahoo.co.in

2. Introduction
 A Computer is an electronic data processing
machine.
 It accepts input data (facts) process them
and produces the required result (the
output).

3. Basic Block Diagram of a Computer
Input Unit CPU Output Unit

4. Organization of a Computer
There are three basic units in a computer.
They are
Input Unit
Output Unit
Central Processing Unit (CPU)

5. CPU is further classified into three Units. They are
 Arithmetic and Logical Unit
 Memory Unit
 Control Unit

6. Organization of a Computer
Arithmetic and
Logical Unit
Memory Unit
Input Unit Output Unit
Control Unit
CENTRAL PROCESSING UNIT

7. Input Unit:
The input unit reads the necessary data
and the instructions given to the
computer.
Most commonly used input device are
mouse and the keyboard.

8. Output Unit:
The Output unit presents the results
obtained by the computer to the
user. The output unit is normally a
printer or a Visual Display Unit.

9. Memory Unit:
The memory unit is used to store
instructions and data that will be
used for computation. Two types
of memory are provided. They
are
 Main Memory
 Auxiliary Memory

10. Main Memory
 Main memory also known as primary memory.
 It is made up of electronic semi-conductor
devices and resides in the Central Processing Unit
(CPU).
 The data stored in the main memory are lost
when the electronic power supply is cut off. This
is called as a volatile memory

11.  RAM is the abbreviation of Random Access Memory. This
is also the computer's main memory where the computer
stores all the data and instructions it receives from input
and the results as it works through its calculation.
 RAM is a short-term memory or volatile memory.
 Random access memory requires some time for access to
each data and is considered to be the fastest memory.

12. Auxiliary memory
Auxiliary memory also known as
secondary memory/non-volatile
memory.
The auxiliary memory has a bulk
storage area.

13.  Magnetic drums magnetic tape and magnetic disks
are some examples of auxiliary memory devices.
 Used to store data permanently and are connected to
the computer system as required.
 Most commonly used auxiliary memories are hard
disk and floppy disk.

14. ROM is the abbreviation of Read Only
Memory.
It is permanently in-built in the
computer at the time of production.
It stores a set of instructions
permanently, which can only be read
and executed.
The information stored in ROM cannot
be altered or erased.

15.  ROM's are non-volatile.
 Variations of this type of memory are available where
flexibility is provided to a certain extent.
 PROM (Programmable Read Only Memory) is a
memory that can be programmed by a user according
to his wish.
 To erase the contents of a PROM and reprogram
another type of ROM called Erasable Programmable
Read only Memory (EPROM) is used.

16. Arithmetic Logic Unit:
The arithmetic logic unit is capable of
performing the operations of addition,
subtraction, multiplication and division as
well as some logical operations like
comparisons.
After the data is processed here, the result
returned to the memory unit for storage.

17. Control Unit:
 The Control unit sequences the operation of the
computer, controlling the actions of all other units.
 The control circuitry interprets the instructions given
to the computer and directs the rest of the machine
its operation.