Search results
Results from the WOW.Com Content Network
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 virtualization, guest operating systems can use hardware that is not specifically made for virtualization. Higher performance hardware such as graphics cards use DMA to access memory directly; in a virtual environment all memory addresses are re-mapped by the virtual machine software, which causes DMA devices to fail.
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.
I/O thereafter proceeds without intervention from the CPU until an event requiring notification of the operating system occurs, at which point the I/O hardware signals an interrupt to the CPU. A channel is an independent hardware component that coordinates all I/O to a set of controllers or devices.
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.
Super I/O (sometimes Multi-IO) [1] is a class of I/O controller integrated circuits that began to be used on personal computer motherboards in the late 1980s, originally as add-in cards, later embedded on the motherboards. A super I/O chip combines interfaces for a variety of low-bandwidth devices. Now it is mostly merged with EC.
A poll message is a control-acknowledgment message.. In a multidrop line arrangement (a central computer and different terminals in which the terminals share a single communication line to and from the computer), the system uses a master/slave polling arrangement whereby the central computer sends message (called polling message) to a specific terminal on the outgoing line.
An example would be from supervisor mode to protected mode. This is where the operating system performs actions like accessing hardware devices or the memory management unit. Generally the operating system provides a library that sits between the operating system and normal user programs. Usually it is a C library such as Glibc or Windows API ...