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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.
In computer science, asynchronous I/O (also non-sequential I/O) is a form of input/output processing that permits other processing to continue before the I/O operation has finished. A name used for asynchronous I/O in the Windows API is overlapped I/O .
When reading from standard program storage, there are no side-effects due to the order of memory read operations. In embedded system programming, it is very common to have memory-mapped I/O where reads and writes to memory trigger I/O operations, or changes to the processor's operational mode, which are highly visible side effects. For the ...
Memory-mapped I/O is preferred in IA-32 and x86-64 based architectures because the instructions that perform port-based I/O are limited to one register: EAX, AX, and AL are the only registers that data can be moved into or out of, and either a byte-sized immediate value in the instruction or a value in register DX determines which port is the source or destination port of the transfer.
The model captures the fact that read and write operations are much faster in a cache than in main memory, and that reading long contiguous blocks is faster than reading randomly using a disk read-and-write head. The running time of an algorithm in the external memory model is defined by the number of reads and writes to memory required. [3]
A GPIO pin's state may be exposed to the software developer through one of a number of different interfaces, such as a memory-mapped I/O peripheral, or through dedicated IO port instructions. Some GPIOs have 5 V tolerant inputs: even when the device has a low supply voltage (such as 2 V), the device can accept 5 V without damage.
Programmed input–output (also programmable input/output, programmed input/output, programmed I/O, PIO) is a method of data transmission, via input/output (I/O), between a central processing unit (CPU) and a peripheral device, [1] such as a Parallel ATA storage device. Each data item transfer is initiated by an instruction in the program ...
In computing, vectored I/O, also known as scatter/gather I/O, is a method of input and output by which a single procedure call sequentially reads data from multiple buffers and writes it to a single data stream (gather), or reads data from a data stream and writes it to multiple buffers (scatter), as defined in a vector of buffers.