Function of Operating Systems. Introduction

1.

Function of
Operating Systems
Introduction

2.

The Operating System MUST:
• provide and manage hardware resources
• provide an interface between the user and the machine
• provide an interface between applications software and the
machine
• provide security for the data on the system
• provide utility software to allow maintenance to be done

3.

IO Functions
• input-output control system

4.

Evolution
Now higher level languages are developed, the OS needs:
• A translator program with:
• Assembler (translates assembly language)
• Compiler (translates high level language)
• Interpreter (translates then runs 1 line at a time)

5.

Memory Management Scheduling
The OS must manage the CPU time so that the user has no
concept of tasks being dealt with individually.

6.

Memory Management Spooling
The I/O phase should not hold up the CPU which can easily
happen when mechanical operations cannot keep up. Eg??

7.

Memory Management - Loader
What happens if you load programs in a different order?
The ‘Loader’ remembers.

8.

Memory Management - Users
What happens if two users want to
use the same program at the same
time?
Programs such as this compiler,
working in the way described, are
called re-entrant.

9.

KEY TERMS
• Memory Management - The process of the operating system
being able to control the use of the computer’s memory,
rather than the user doing it
• Scheduling - When there is more than one thing which could
be done at a time something has to decide what will be done
first.
• Spooling - store all input and output on a high-speed device
such as a disk until the slower peripheral device is ready.