- In addition to the processor and a set of memory modules, the third key element of a computer system is a set of input-output subsystem referred to as I/O, provides an efficient mode of communication between the central system and the outside environment.
- Programs and data must be entered into computer memory for processing and results obtained from computations must be recorded or displayed for the user.
- Devices that are under the direct control of the computer are said to be connected on- These devices are designed to read information into or out of the memory unit upon command from CPU.
- Input or output devices attached to the computer are also called peripherals.
- Among the most common peripherals are keyboards, display units, and printers.
- Perhaps those provide auxiliary storage for the systems are magnetic disks and tapes.
- Peripherals are electromechanical and electromagnetic devices of some complexity.
- We can broadly classify peripheral devices into three categories:
- Human Readable: Communicating with the computer users, g. video display terminal, printers etc.
- Machine Readable: Communicating with equipments, g. magnetic disk, magnetic tape, sensor, actuators used in robotics etc.
- Communication: Communicating with remote devices means exchanging data with that, e.g. modem, NIC (network interface Card) etc.
Fig: Block diagram of Peripheral device
- Control signals determine the function that the device will perform such as send data to I/O module, accept data from I/O module.
- Status signals indicate the state of the device e. device is ready or not.
- Data bits are actual data transformation.
- Control logic associated with the device controls the device's operation in response to direction from the I/O module.
- The transducer converts data from electrical to other forms of energy during output and from other forms to electrical during input.
- Buffer is associated with the transducer to temporarily hold data being transferred between the I/O module and external devices e. peripheral environment.
Input Device
- Keyboard
- Optical input devices
- Card Reader
- Paper Tape Reader
- Optical Character Recognition (OCR)
- Optical Bar code reader (OBR)
- Digitizer
- Optical Mark Reader
- Magnetic Input Devices
- Magnetic Stripe Reader
- Magnetic Ink Character Recognition (MICR)
- Screen Input Devices
- Touch Screen
- Light Pen
- Mouse
- Analog Input Devices
Output Device
- Card Puncher, Paper Tape Puncher
- Monitor (CRT, LCD, LED)
- Printer (Impact, Ink Jet, Laser, Dot Matrix)
- Plotter
- Analog
- Voice