I/O MANAGEMENT TOPIC 6

Question 1

I/O Devices: External devices

Answer 1

• Human readable eg. Printers, keyboards
• Machine readable - actuators, disk and tape drivers.
• Communications- Moderns

Question 2

Organisation of the I/O function

Answer 2

1. Programmed I/O
2. Interrupt-Driven I/O
3. Direct Memory Access

Question 3

Evolution of the I/O function

Answer 3

• The processor directly controls a peripheral device

Question 4

Direct Memory Access

Answer 4

1. Data count
2. Data register
3. Address register
4. Control logic

Question 5

Types of DMA configurations:

Answer 5

1. Single Bus detached DMA
   - Processor-DMA-I/O-I/O-Memory
2. Single Bus, integrated of DMA-I/O
   - Processor-DMA-DMA-Memory
3. System Bus
   Processor- DMA- Memory
4. I/O Bus I/O-I/O-I/O

Question 6

I/O Buffering

Answer 6

• Buffering is required when a user process wants to rad blocks of data from a disk
• It waits either by:
  Busy waiting
  Process suspension of an interrupt

Question 7

Types of I/O devices

Answer 7

1. Block-oriented
   - stores information in blocks that are usually fixed in size
2. Stream-oriented
   - Transfers data in and out as a stream of bytes