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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. Inputs are the signals or data received by the system and outputs are the signals or data sent from it.
The port numbers in the range from 0 to 1023 (0 to 2 10 − 1) are the well-known ports or system ports. [3] They are used by system processes that provide widely used types of network services. On Unix-like operating systems, a process must execute with superuser privileges to be able to bind a network socket to an IP address using one of the ...
In the original S/360 and S/370 architectures, each processor had its own set of I/O channels and addressed I/O devices with a 12-bit cuu address, containing a 4-bit channel number and an 8-bit unit (device) number to be sent on the channel bus in order to select the device; the operating system had to be configured to reflect the processor and ...
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.
For TCP, port number 0 is reserved and cannot be used, while for UDP, the source port is optional and a value of zero means no port. A process associates its input or output channels via an internet socket, which is a type of file descriptor, associated with a transport protocol, a network address such as an IP address, and a port
A common example is a graphics processing unit. accumulator A register that holds the result of previous operation in ALU. It can be also used as an input register to the adder. address The unique integer number that identifies a memory location or an input/output port in an address space. address space
Each device can request up to six areas of memory space or input/output (I/O) port space via its configuration space registers. In a typical system, the firmware (or operating system ) queries all PCI buses at startup time (via PCI Configuration Space ) to find out what devices are present and what system resources (memory space, I/O space ...
The name originates from the Basic Input/Output System used in the CP/M operating system in 1975. [ 2 ] [ 3 ] The BIOS firmware was originally proprietary to the IBM PC ; it was reverse engineered by some companies (such as Phoenix Technologies ) looking to create compatible systems.