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| {{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 ]. For other uses of the term "I/O"|I/O (disambiguation)}} | |||
| {{about||uses of the term input-output in economics|Input-output model|the medical term|Toileting#Input and output}} | |||
| In ], '''input/output''', or '''I/O''', refers to the communication between an ] (such as a ]), and the outside world – possibly a human, or another information processing system. ]s are the signals or data received by the system, and ]s 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 ]. I/O devices are used by a person (or other system) to communicate with a computer. For instance, ]s and ] are considered input devices of a computer, while ]s and ]s are considered output devices of a computer. Devices for communication between computers, such as ]s and ]s, typically serve for both input and output. | In ], '''input/output''', or '''I/O''', refers to the communication between an ] (such as a ]), and the outside world – possibly a human, or another information processing system. ]s are the signals or data received by the system, and ]s 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 ]. I/O devices are used by a person (or other system) to communicate with a computer. For instance, ]s and ] are considered input devices of a computer, while ]s and ]s are considered output devices of a computer. Devices for communication between computers, such as ]s and ]s, typically serve for both input and output. | ||
Revision as of 23:04, 21 September 2009
"I/O" redirects here. For other uses, see I/O (disambiguation). For uses of the term input-output in economics, see Input-output model. For the medical term, see Toileting § Input and output.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.
Interface
I/O Interface is not required when the I/O device is driven by the processor. The interface must have necessary 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 ; 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 required
A computer that uses memory-mapped I/O accesses hardware by reading and writing to specific memory locations, system]] and programming facilities employ separate, more abstract I/O concepts and [[languages, and operating systems in the Unix family, traditionally abstract files and devices as [[stream (functions for manipulating streams for input and output.
In the context of the ALGOL 68 programming language, the input and output facilities are An alternative to special
Addressing mode
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 and addressing.
Direct address
In this type of address of the data is a part of the instructions itself. When the processor decodes the instruction, it doesn't gets the memory address from where it can be read/store the required information.
Mov Reg.
Here the Addr operand points to a memory location which holds the data and copies it into the specified Reg.
Indirect address
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.
Port-mapped I/O
Port-mapped I/O usually requires the use of instructions which are specifically designed to perform I/O operations.