This presentation is targeted towards the student of Class 11 and 12 in Nepal and India,

1. Compiled and Prepared By:
Mandip Bhattarai
Kasturi College, Itahari Nepal
For Queries and Feedback
lackofmind69@gmail.com
Mandip.bhattarai@facebook.com
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Computer System

2. Definition
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 A computer system is a
combination of different computer
hardware and software that work
together to achieve the purpose of
the instruction or program.
 In other words, a computer system
is a set of hardware and software
which process data in a meaningful
way.

3. 3

4. Input Unit Output Unit
Secondary Memory
CU
ALU
Primary Memory
- - - - - - Control Flow
______________ Data flow
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5. Functioning of Computer
System
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 In a computer system when user gives
input through the input devices if first
goes to the Primary memory and then
send to the ALU for the further
processing and then processed data
again send to primary memory if needed
then to output units.
 These all happens in the direction of
Control Unit.

6. Components of Computer
System
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 Input Unit
 Primary Memory
 Arithmetic Logic Unit
 Control Unit
 Secondary Memory
 Output Unit

7. Input Unit
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 Input Units are the media through which user
communicate with the computer.
 An input unit perform the following operation
sequentially:
 It accepts or reads the list of instruction and
data from the user.
 It converts the received data into the computer
understandable form.
 It supplies the converted data into computer
system.
 Some of the input devices are Keyboard, Mouse,
Scanner, Microphone etc.

8. Central Processing Unit
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 It is the only part of computer where all
processing takes place.
 It works with Operating system and
executes the set of instruction, control
different peripherals devices by sending
and receiving the control signals.
 The CPU is made up of 3 major units:
ALU, CU and Primary memory.

9. Arithmetic Logical Unit
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• All the arithmetic and logical operation are
performed in this unit under the direction of
control unit.
• ALU performs the following tasks:
 It performs the arithmetic operation on data
like addition, subtraction, multiplication,
division, modulation.
 It performs the logical operation or
comparisons such as less than, equal to,
greater than , AND, OR, NOT,etc.

10. Control Unit
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 Control unit co-ordinate the flow of data in and out of
the ALU, the primary memory, the secondary
memory, and various input and output devices.
 The Jobs of Control unit can be listed as follows:
 Send the input from input devices to the
memory unit.
 Gets the instruction from memory unit.
 Decodes the instruction or determine the
instruction.
 Gets the data required by the instruction.
 Activates the right circuit for the instruction to
be obeyed.

11. Memory Unit
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 The primary memory is the working space where
unprocessed data (data to be processed),
instruction or program currently running and
processed data (information) are temporarily
stored.
 The function of memory unit are as follows:
 It holds all data to be processed and the
instruction required for processing.
 It stores intermediate result of processing.
 It stores the final result of processing
before these results are released to output
devices.

12. Output Unit
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 The output devices show the result of
processing and other information from the
computer to the user in the human
understandable form.
 The output unit performs the following
functions:
 It accepts the result produced by the
computer, which are in binary form.
 It converts the binary form result to human
understandable form.
 It supplies the converted result to the user.

13. Layer of Computer Architecture
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Application Software Layer
System Software Layer
Hardware Layer
Microprogram Layer
Digital Logic Layer
Electrical and Electronic
Component Layer