Consists of input devices and output devices.
Techniques
Section titled “Techniques”Programmed I/O
Section titled “Programmed I/O”- CPU has direct control over I/O
- Continuously sense status – Poll
- Read/write commands
- Transferring data
- CPU waits for I/O module to complete operation
- Wastes CPU time
Interrupt Driven I/O
Section titled “Interrupt Driven I/O”CPU does its own work without waiting. When I/O device is ready, interrupts CPU.
Steps:
- CPU issues read command
- I/O module gets data from peripheral whilst CPU does other work
- I/O module interrupts CPU
- CPU requests data
- I/O module transfers data
Direct Memory Access (DMA)
Section titled “Direct Memory Access (DMA)”DMA transfers data directly to/from memory without CPU intervention.