COMPUTER SYSTEM (CLASS - XI) (PART - 2)

COMPUTER SYSTEM

OUTPUT UNIT

The output unit is formed by the output devices attached to the computer. The output coming from the CPU is in the form of electronic binary signals which needs conversion on some form which can be easily understand by human. The function of conversion is performed by output units.

Another words we say, A device that can receive data from computer or another device and create output with data is called output device.

Some output devices are:

Monitor: A monitor is an output device that is responsible for receiving data from computer and displaying that information as characters, graphical and audio visual form for users to see.

Speakers: It receive the sound in the form of electric current from the sound card and then convert it to sound format audible to users.

Printers: It is the device that deliver information by means of printed characters on paper.

Projector: Gets data from a computer and displays or projects the same information onto a screen or a wall. Projector cannot directly accept data from a user and send that data to another device.

INPUT/OUTPUT DEVICES

An I/O device is capable of receiving data from users or other devices and also sending data to another devices or computers. That means a device which can be used as both input device and output device are called I/O devices. Examples:

USB (Universal Serial Bus): Also known as pen drive or flash stick works as both input device to computer and as an output device. USB drives receive or save data from a computer as an input and it can also send data to a computer or another device.

Modems (Modulator-demodulator): It is used to transmit and receive data from one computer to another computer or other devices using telephone lines.

Facsimile: Facsimile or FAX machine has a scanner which is an input device and a small printer to provide output.

Handset: Handset consists of speaker as an output device and microphone function as an input device.

Touch Screen: Touch screen is both input and output device. By touching screen input is provided and being a screen, it is used as an output device.

 CPU (Central Processing Unit)

It is also called brain of the computer as it guides, directs, controls and governs the performance of a computer. The CPU has some sub-complements that help in carrying out the processing task.

These are:

1.Arithmetic Logic Unit (ALU)

2.Control Unit (CU)

3.Registers

Arithmetic Logic Unit (ALU): The ALU performs all the arithmetic operations like addition, subtraction, multiplication & subtraction and some logical operations like (<, >, =, <=, >=, !=).

Control Unit (CU): Control Unit acts as a supervisor by controlling and guiding the operation taking place.

Registers: Registers or Processor registers are small units of data holding places. ALUs have a small amount of special storage units called registers that can be accessed faster than main memory.

Memory: A collection of cells, each with a unique physical address. The memory of computer is often called main memory or primary memory.

The memory of a computer can be thought of as ‘cells’. Each of these cells is further broken down into smaller part known as bits. A bit means a binary digit i.e., either 0 or 1. A number of bits together are used to store data instructions by their combination.