Output Devices

Computer Output Function

The computer output function is an activity in which a computer communicates information to the user in the form of text or images on the screen or paper, sound/audio or video. Several kinds of equipment (devices and media) are used for computer output.

Many of these are described in the next posts.

An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by a computer system to the outside world.

The most common output devices are:

• Visual display units (monitors),
• Printers,
• Speakers.

An output device is not directly accessible to the CPU but is connected to it through some circuitry called an interface on the computer’s central electronic wiring called the motherboard or parent board. Interfaces include addressable ports.

A device may have its own controller that supervises the operations of the particular device. Each peripheral (including output-) device has its own associated interface unit. The interface decodes the address and control signal received from the I/O bus, interprets them for the peripheral, and provides signals for the peripheral controller. It also synchronizes the data flow and supervises the transfer between peripheral and processor. Each peripheral has its own controller that operates the particular electromechanical device. For example, the printer controller controls the paper motion, the print timing, and the selection of printing characters. A controller may be housed separately or may be physically integrated with the peripheral.
To communicate with a particular device, the processor places a device address on the address lines. Each interface attached to the I/O bus contains an address decoder that monitors the address lines. When the interface detects its own address, it activates the path between the bus lines and the device that it controls. Any peripheral whose address does not correspond to the address in the bus is isolated by its interface. At the same time that the address is made available on the address lines, the processor provides a function code in the control lines. The interface selected responds to the function code and proceeds to execute it.

Click here to read about Computer monitors as an output device.

Click here to read about Characteristics of computer monitor.