input/output
{{cleanup-reorganize|date=June 2007}}{{unreferenced|date=June 2007}}{{Redirect7|
I/O,
I/O device,
I/O interface,
Read/write channel, and
Transput all|the use of the term
input-output in economics |Input-output model|the medical term, see
Toileting#Input and output. For other uses of the term
I/O|I/O (disambiguation)}}In
computing,
input/output, or
I/O, refers to the communication between an
information processing system (such as a
computer), and the outside world – possibly a human, or another information processing system.
Inputs are the signals or data received by the system, and
outputs are the signals or data sent from it. The term can also be used as part of an action; to "perform I/O" is to perform an
input or output operation. I/O devices are used by a person (or other system) to communicate with a computer. For instance,
keyboards and
mouses are considered input devices of a computer, while
monitors and
printers are considered output devices of a computer. Devices for communication between computers, such as
modems and
network cards, typically serve for both input and output.Note that the designation of a device as either input or output depends on the perspective. Mouses and keyboards take as input physical movement that the human user outputs and convert it into signals that a computer can understand. The output from these devices is input for the computer. Similarly, printers and monitors take as input signals that a computer outputs. They then convert these signals into representations that human users can see or read. (For a human user the process of reading or seeing these representations is receiving input.)In computer architecture, the combination of the
CPU and
main memory (i.e. memory that the CPU can read and write to directly, with individual
instructions) is considered the brain of a computer, and from that point of view any transfer of information from or to that combination, for example to or from a
disk drive, is considered I/O. The CPU and its supporting circuitry provide
memory-mapped I/O that is used in low-level
computer programming in the implementation of
device drivers. Higher-level
operating system and programming facilities employ separate, more abstract I/O concepts and
primitives. For example, most operating systems provide application programs with the concept of
files. The
C and
C++ programming languages, and operating systems in the
Unix family, traditionally abstract files and devices as
streams, which can be read or written, or sometimes both. The
C standard library provides
functions for manipulating streams for input and output.
- Transput - In the context of the ALGOL 68 programming language, the input and output facilities are collectively referred to as transput. The ALGOL 68 transput library recognizes the following standard files/devices:
stand in, stand out, stand error and stand back.
An alternative to special primitive functions is the I/O
monad, which permits programs to just describe I/O, and the actions are carried out outside the program. This is notable because the I/O functions would introduce
side-effects to any programming language, but now
purely functional programming is practical.
I/O InterfaceI/O Interface is required whenever the I/O device is driven by the processor. The interface must have necessory logic to interpret the device address generated by the processor.Handshaking should be implemented by the interface using appropriate commands like (BUSY,READY,WAIT) the processor can communicate with I/O device through the interface.If incase different data formated being exchanged; interface must be able to convert serial data to parallel form and vice-versa.There must be provision for generating
interrupts and the corresponding type numbers for further processing by the processor if requiredA computer that uses
memory-mapped I/O accesses hardware by reading and writing to specific memory locations, using the same assembler language instructions that computer would normally use to access memory.
Addressing modes
There are many ways through which data can be read or stored in the memory. Each method is an addressing mode, and has its own advantages and limitations.There are many type of addressing modes such as direct addressing, indirect addressing, immediate addressing, index addressing, based addressing, based-index addressing, implied addressing, etc.
Direct addressing
In this type of address of the data is a part of the instructions itself. When the processor decodes the instruction, it gets the memory address from where it can be read/store the required information.Mov Reg. [Addr]Here the
Addr operand points to a memory location which holds the data and copies it into the specified Reg.
Indirect addressing
Here the address can be stored in a register. The instructions will have the register which has the address. So to fetch the data, the instruction must be decoded appropriate register selected. The contents of the register will be treated as the address using this address appropriate memory location is selected and data is read/written.
Port-mapped I/O
Port-mapped I/O usually requires the use of instructions which are specifically designed to perform I/O operations.
See also
Toevoer/afvoerUlaz/izlazVstup/výstupI/OEingabe und AusgabeI/OΣυσκευή εισόδουEntrada/salidaSarrera-irteerako unitateEntrées-sortiesЕнгізу-шығару құрылғысы입출력Ulazno/izlazne jediniceI/OInput/outputIšvesties įrenginysI/O入出力I/OI/OВвод/выводUlaz/IzlazSiirräntäI/OI/OВведення-виведенняI/O
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