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. Computing is usually defined like the activity of using and developing Computer technology Computer hardware and software. An information processor or information processing system, as its name suggests is a System (be it Electrical, Mechanical or Biological A computer is a Machine that manipulates data according to a list of instructions. Inputs are the signals or data received by the system, and outputs are the signals or data sent from it. Input is the term denoting either an entrance or changes which are inserted into a System and which activate/modify a Process. Output is the term denoting either an exit or changes which exit a System and which activate/modify a Process. 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 Scheduling is the term used to describe the method computer operating systems decide the order that block I/O operations will be submitted to the disk subsystem 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. In Computing, a keyboard is an Input device partially modelled after the typewriter keyboard which uses an arrangement of buttons or keys In Computing, a mouse (plural mice, mouse devices, or mouses) A visual display unit, often called simply a monitor or display, is a piece of Electrical equipment which displays images generated from the Video Devices for communication between computers, such as modems and network cards, typically serve for both input and output. Modem (from mo dulator- dem odulator is a device that modulates an analog carrier signal to encode Digital information A Network card, Network Adapter, LAN Adapter or NIC (network interface card is a piece of Computer hardware designed to allow computers

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. Computer data storage, often called storage or memory, refers to Computer components devices and recording media that retain digital e. memory that the CPU can read and write to directly, with individual instructions) is considered the heart 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. In Computer science, an instruction is a single operation of a processor defined by an Instruction set architecture. Disk storage is a general category of a Computer storage mechanisms in which data is recorded on planar round and rotating surfaces ( disks, discs, or 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. Memory-mapped I/O ( MMIO) and port I/O (also called port-mapped I/O or PMIO) are two complementary methods of performing Input/output In computing a device driver or software driver is a Computer program allowing higher-level computer programs to interact with a Hardware device

Higher-level operating system and programming facilities employ separate, more abstract I/O concepts and primitives. An operating system (commonly abbreviated OS and O/S) is the software component of a Computer system that is responsible for the management and coordination In Computer science, primitive types — as distinct from Composite types ' — are Data types provided by a Programming language as basic For example, most operating systems provide application programs with the concept of files. A computer file is a block of Arbitrary Information, or resource for storing information which is available to a Computer program and is usually The C and C++ programming languages, and operating systems in the Unix family, traditionally abstract files and devices as streams, which can be read or written, or sometimes both. tags please moot on the talk page first! --> In Computing, C is a general-purpose cross-platform block structured C++ (" C Plus Plus " ˌsiːˌplʌsˈplʌs is a general-purpose Programming language. Unix (officially trademarked as UNIX, sometimes also written as Unix with Small caps) is a computer In computing the term stream is used in a number of ways in all cases referring to a succession of data elements made available over time The C standard library provides functions for manipulating streams for input and output. The C standard library (also known as libc) is a now-standardized collection of Header files and library routines used to implement common operations such The C programming language provides many Standard library functions for file input and output.

• Transput - In the context of the ALGOL 68 programming language, the input and output facilities are collectively referred to as transput. Time-line of ALGOL 68 The Algorithmic Language ALGOL 68 Reports Mar The ALGOL 68 transput library recognizes the following standard files/devices: stand in, stand out, stand error and stand back.

An alternative to special primitive functions is the I/O monad, which permits programs to just describe I/O, and the actions are carried out outside the program. In Functional programming, a monad is a kind of Abstract data type used to represent Computations (instead of data in the Domain model) This is notable because the I/O functions would introduce side-effects to any programming language, but now purely functional programming is practical. In Computer science, a function or expression is said to produce a side effect if it modifies some state in addition to returning a value Purely functional is a term in Computing used to describe Algorithms Data structures or Programming languages that exclude destructive modifications

I/O Interface

I/O Interface is required whenever the I/O device is driven by the processor. The interface must have necessory 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 communicate with I/O device through the interface.

If incase different data formated being exchanged; interface must be ablt 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

Memory-mapped I/O

A computer that uses memory-mapped I/O accesses hardware by reading and writing to specific memory locations, using the same assembler language instructions that computer would normally use to access memory. In Computing, an interrupt is an asynchronous signal from hardware indicating the need for attention or a synchronous event in software indicating the need for a change Memory-mapped I/O ( MMIO) and port I/O (also called port-mapped I/O or PMIO) are two complementary methods of performing Input/output

Addressing Modes

There are many ways to through which data can be read,stored in the memory. Each method has its own advantages and limitations. The concept is called addressing modes. In short, different ways to fetch an operand is the addressing mode.

There are many type of addressing modes like direct addressing, indirect addressing, immediate addressing, index addressing, based addressing, based-index addressing, implied addressing,etc.

Direct Addressing

In this type of address of the data is a part of the instructions itself. When the processor decodes the instruction, it gets the memory address from where it can be read/store the required information.

Mov Reg. [Addr]

Here the Addr operand points to a memory location which holds the data and copies it into the specified Reg.

Indirect Addressing

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. The contents of the register will be treated as the address using this address appropriate memory location is selected and data is read/written.

Port-mapped I/O

Port-mapped I/O usually requires the use of instructions which are specifically designed to perform I/O operations. Memory-mapped I/O ( MMIO) and port I/O (also called port-mapped I/O or PMIO) are two complementary methods of performing Input/output

See also

• C file input/output