Chapter 10. Operating Systems. Software Categories. Software Categories. Application software is written to address our specific needs—to solve problems in the real world.
Within the class of system software are two categories:
Figure 10.1 An operating system interacts with many aspects of a computer system.
Resource management consists of:
Figure 10.3 Memory is a continuous set of bits referenced by specific addresses
A program may include instructions that transfer control. For example, in BASIC a programmer can say
where 200 is the line number of the instruction to be executed next.
This line number is relative to the start of the program and so is a logical address.
However, the physical address is the actual location in memory where this instruction is stored.
Figure 10.4 Main memory divided into two sections
Figure 10.5 binding a logical address to a physical one
Figure 10.6 Address resolution in partition memory management
Figure 10.7 A paged memory management approach
Figure 10.2 In early systems, human operators would organize jobs into batches
Figure 10.8 The process life cycle
In each of the following examples we will consider 5 processes arriving in the Ready state. The service time for each is listed in this table.
How does the dispatcher decide their order?
The same 5 processes produce a much smaller average turn around time. SJN is provably optimal as a strategy.
It’s weakness is that it relies on knowledge of the future.
Suppose the time slice is 50.
This Gannt Chart shows how the processes will be scheduled.