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In computing, input/output (I/O, i/o, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, such as another computer system, peripherals, or a human operator. Inputs are the signals or data received by the system and outputs are the signals or data sent from it.
In computing, an input device is a piece of equipment used to provide data and control signals to an information processing system, such as a computer or information appliance. Examples of input devices include keyboards, computer mice, scanners, cameras, joysticks, and microphones. Input devices can be categorized based on: modality of output ...
A display device is the most common form of output device which presents output visually on computer screen. The output appears temporarily on the screen and can easily be altered or erased. With all-in-one PCs, notebook computers, hand held PCs and other devices; the term display screen is used for the display device.
Common examples include keyboards and mice (input) and displays and printers (output). Network interface controllers are used to access the Internet . [ 64 ] USB ports also allow power to connected devices—a standard USB supplies power at 5 volts and up to 500 milliamps (2.5 watts ), while powered USB ports with additional pins may allow the ...
For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, [1] [2] although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it.
The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a fieldbus or computer network that plugs into the PLC. The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control , distributed control systems , and networking .
When using any of these gate setups the overall system has memory; it is then called a sequential logic system since its output can be influenced by its previous state(s), i.e. by the sequence of input states. In contrast, the output from combinational logic is purely a combination of its present inputs, unaffected by the previous input and ...
An IOCS program must create a control block for each file, specifying information unique to the file. For 7070 IOCS these are entries in the File Specification Table for tape files, each of which is generated by a DTF [7]: 19–26 [15]: 26–28 statement, or separate control blocks generated by DDF [8]: 31–37 [15]: 29–30 or DUF [7]: 44–47 [15]: 31–33 statements.