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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.
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 ...
Input and output voltages are usually, but not always, limited to the supply voltage of the device with the GPIOs, and may be damaged by greater voltages. 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 ...
How to select a LUN: In the early versions of SCSI, an initiator delivers a Command Descriptor Block (CDB) to a target (physical unit) and within the CDB is a 3-bit LUN field to identify the logical unit within the target. In current SCSI, the initiator delivers the CDB to a particular logical unit, so the LUN appears in the transport layer ...