Chapter 6
Computer Organizaton II
Tutorial 18

1.	Describe the characteristics and the usage of the following input devices:

Keyboard
Mouse
Trackball
Touch pad
Touch Screen
Scanner
Microphone

2.	Describe the principals of the following printers:

Dot-matrix printer
Laser printer
Ink-jet printer

3.	Describe the characteristics and the usage of the following output devices:

VDU
Plotter
Data projector

Chapter 6
Computer Organizaton II
Tutorial 19

1.	Briefly explain why I/O interface is needed.

2.	Briefly explain the three methods of I/O interfacing.

3.	What are the advantages and disadvantages of the above I/O interfacing methods?

Answer

1.	Reasons:

•	Operations of I/O devices are different from the operations of CPU and memory.  In addition, the operations of different peripheral devices are different.  Consequently, the data format and word lengths are different.  Therefore, a conversion of signal values for each device may be required.

•	The data transfer rate of these devices are much slower than that of the memory or CPU.  Therefore, direct connection to the system bus is impractical.

2.	Refer to lecture notes.

3.	
	Advantages	Disadvantages	
Separate buses for memory and I/O	•	Fast in accessing I/O devices
•	Separate I/O instructions, reduced program size
•	Fast in execution.	•	Separate IOP required
•	Extra set of buses required	
Isolated I/O	•	Separate I/O instructions, reduced program size
•	Fast in execution.	•	Extra Read / Write control required	
Memory-mapped I/O	•	Simple architecture
•	All memory instructions available to I/O devices	•	Some memory spaces cannot be used.