Peripheral devices | Computer Architecture & Organisation (CAO) - Computer Science Engineering (CSE) PDF Download

Peripheral devices

• 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 online. 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, e.g. video display terminal, printers etc.
  • Machine Readable: Communicating with equipments, e.g. magnetic disk, magnetic tape, sensor, actuators used in robotics etc.
  • Communication: Communicating with remote devices means exchanging 

• 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 i.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 i.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