Page 61 - Computer - 9(A&B)

For example, if we want to add the numbers 5 and 20, we need to type the numbers and give the instruction
to add them (input). The computer will add them (process) and give the result as the sum of the two numbers
(output).

5, 20, Add 5 + 20 25

Input Process Output
As of now, we know that computer works in the IPO cycle to convert the raw data into useful information. It has
four main functions to perform:
 Input: Accepts data and instructions.

 Processing: Manipulates data as per instructions.
 Output: Produces desired output/information.
 Storage: Stores data, instructions and information.
The basic structure of a computer system consists of various components:

Input CU Output

ALU
CPU

Memory Unit

Control Signals
External Memory Data Flow
During the fi rst stage, computer reads the data and instructions using input device and stores then into the main
memory of the system, which is processed by ALU during the second stage. The results produced by the ALU
are stored back into the memory unit. During the third stage, results are received on the output unit. The data
fl ow in the computer system is controlled by the CU with the help of control signals sent by it to the various
components of the computer system.

Input Devices
The Input devices are attached to the computer system to enter user data and instruction that is to be processed.
As the computer understands only binary data, it is the responsibility of the input devices to convert the data
into the binary form before storing it into the computer. Computer, being a versatile machine, is capable of
processing different forms of data like text, graphics, sound, video, etc.
Let’s discuss some of the commonly used input devices one by one.

Keyboard

This is one of the most commonly used input devices attached to the
computer. It is used to enter textual data in the form of letters, digits
and symbols.
A standard keyboard contains 104 keys in it. These keys when pressed,
generate a digital code that helps the system to understand which key
has been pressed.

Mouse

This is one of the pointing devices used to work in the graphical environment with the help of a pointer moving
on the screen. It works on the principle of ‘Point’ and ‘Click’. It is a hand held device with a rubber ball at its
bottom which when rolled on a fl at surface generates the electrical signals with the help of electrical circuit

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