Input/output

With Ein-/Ausgabe (abbreviated I / O, english input / output, in short I / O ) is defined as - a term from the computer or the computer science - the communication / interaction of an information system with its ' outside world ', eg its users or other information systems, and activities for reading and writing data. Inputs are signals (eg, command line ) or data received by the system, output is sent by the system.

What the ' outside world ' is, depends on the particular viewing from: From the perspective of the computer as an executive processor are, for example, the programs ' inputs '. In a program (this is generally the object of observation ) are application data or information from users and other ' systems ' most important inputs or outputs; for subroutines are, inter alia, also call and return values ​​(parameters) for a printer, it is the information to be printed, including belonging to control commands.

Basics

Input and output is important to allow the application running on the computer programs, an interface to the " outside world ." Thus, a reasonable use of the system is only possible.

For the interaction between the user and the program external peripheral devices available that through the operating system (such as the system bus and / or device drivers) and mechanical or other electronic communication links are operated and controlled. This is necessary because there are many different protocols and the devices can distinguish word length, and processing speed with respect.

The methodology for software development, a distinction is related to inputs and outputs, whether data or information flow or whether data is stored or read in the system from the outside (eg users ) to the system ( or vice versa), should be amended or deleted ( create, read, update, delete = CRUD).

Hardware

The processor responds to external devices via I / O controller ( less powerful but cheaper ) or I / O processors (very powerful but more expensive). These serve as an abstraction layer and are controlled by the CPU with simple READ (READ) and WRITE (WRITE) command. The devices themselves are directly connected by data, control and address buses. They contain buffers to cache requests and responses.

To perform this communication are Programmed Input / Output, interrupt -driven I / O, and DMA available.

For users, the input devices usually keyboard, mouse and joystick, output devices are mostly screen, printer or portable storage media such as CDs, etc.

In relation to the environment can also input sensors ( for temperature, speed, pressure ...) means. The output would then be, for example, power controller, valve controllers, etc. In the area of ​​control and measurement technology as something is used.

Software

In software, we can distinguish the input in command line, enter in the program from keyboard, mouse or joystick - query, read-only access to a storage medium or direct write access to an A / D converter or the like.

The software- edition runs generally not on the command line, but only in the program as write access to screen, printer, memory, or an A / D converter or the like.