Principle of Input/Output Software
Goals of I/O Software
Key Issues in the Design of I/O Software (page 352):
 Device independence
 Uniform naming
 Error handling
 Synchronous (blocking) versus asynchronous (interrupt-driven) transfer

Buffering

Shared and dedicated devices: the O.S must be able to handle both shared and dedicated
devices in a way that avoids problems.
Input / Output Layers (Figure 5.11, page 356)
User-Level I/O Software
Device-Independent I/O Software
Device drivers
Interrupt handlers
Hardware
Functions done in the device independent software: (Figure 5.13, Page 361)
Main functions of each layer (Figure 5.17, page 368)
Chapter 5 Questions
1
a)
b)
c)
2.
What are the key concepts used in the design of I/O software?
What are the four layers in which I/O software are structured?
What is the function of each of these layers?
Do exercise 14, page 430.