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349:. A further complication is that a device traditionally considered an input device, e.g., card reader, keyboard, may accept control commands to, e.g., select stacker, display keyboard lights, while a device traditionally considered as an output device may provide status data (e.g., low toner, out of paper, paper jam).
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should be implemented by the interface using appropriate commands (like BUSY, READY, and WAIT), and the processor can communicate with an I/O device through the interface. If different data formats are being exchanged, the interface must be able to convert serial data to parallel form and vice versa.
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accesses hardware by reading and writing to specific memory locations, using the same assembly language instructions that computer would normally use to access memory. An alternative method is via instruction-based I/O which requires that a CPU have specialized instructions for I/O. Both input and
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The designation of a device as either input or output depends on perspective. Mice and keyboards take physical movements that the human user outputs and convert them into input signals that a computer can understand; the output from these devices is the computer's input. Similarly, printers and
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requires the use of instructions that are specifically designed to perform I/O operations. The I/O instructions address the channel or the channel and device; the channel asynchronously accesses all other required addressing and control information. This is similar to DMA, but more flexible.
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also requires the use of special I/O instructions. Typically one or more ports are assigned to the device, each with a special purpose. The port numbers are in a separate address space from that used by normal instructions.
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monitors take signals that computers output as input, and they convert these signals into a representation that human users can understand. From the human
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Because it would be a waste for a processor to be idle while it waits for data from an input device there must be provision for generating
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364:, is considered the brain of a computer. Any transfer of information to or from the CPU/memory combo, for example by reading data from a
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is one designed to exploit locality and perform efficiently when exchanging data with a secondary storage device, such as a disk drive.
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An I/O interface is required whenever the I/O device is driven by a processor. Typically a CPU communicates with devices via a
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sent from it. The term can also be used as part of an action; to "perform I/O" is to perform an
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rate that can vary greatly. With some devices able to exchange data at very high speeds
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and the corresponding type numbers for further processing by the processor if required.
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used by a human (or other system) to communicate with a computer. For instance, a
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and programming facilities employ separate, more abstract I/O concepts and
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to memory (DMA) without the continuous aid of a CPU is required.
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and the reaction the system responds is called the output.
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The
Essentials of Computer Organization and Architecture
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The I/O facilities provided by operating systems may be
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Fundamentals of
Computer Organization and Architecture
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An alternative to special primitive functions is the
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352:In computer architecture, the combination of the
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605:Abd-El-Barr, Mostafa; Hesham El-Rewini (2005).
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567:. Jones & Bartlett Learning. p. 185.
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464:to any programming language, but this allows
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30:"I/O" redirects here. For other uses, see
127:Learn how and when to remove this message
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656:at Wikimedia Commons
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61:improve this article
32:I/O (disambiguation)
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117:November 2019
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59:Please help
54:verification
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629:11 December
585:11 December
488:Channel I/O
483:Channel I/O
402:Handshaking
358:main memory
293:I/O devices
189:File system
574:0763737690
545:References
439:primitives
407:interrupts
366:disk drive
199:Networking
179:Interrupts
87:newspapers
18:I/O device
529:I/O bound
454:I/O monad
447:functions
392:Interface
249:computing
664:Category
623:Archived
579:Archived
518:See also
319:printers
315:monitors
303:keyboard
299:hardware
273:computer
204:Security
477:records
101:scholar
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309:is an
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384:. An
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108:JSTOR
94:books
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356:and
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80:news
458:I/O
398:bus
354:CPU
305:or
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261:i/o
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