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3.1 - The Function of
Operating Systems
- The main features of operating systems
- An OS 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
- Provide and manage hardware resources
- Original purpose was to prevent
duplication of code by providing
input and output resources
- Prevents each individual program
from having code to control input
and output (duplication of code)
- Input-Output Control System (IOCS)
- Prevents each individual program
from having code to control input
and output (duplication of code)
- Development of
assembly/high level
languages means that OS
needed:
- A translator
program to turn
human friendly code
into computer
friendly code
- Assembler - Handles translation from assembly
language
- Compiler - Translates high level code into object
code
- Interpreter - Translates a line of high level code
and runs the result before translating the next
line
- Assembler - Handles translation from assembly
language
- A translator
program to turn
human friendly code
into computer
friendly code
- Memory management
- More than one program
should be stored in memory
and the processor should give
time to each of the programs
- Processor should give time to each of the
programs and process higher priority
processes first of all
- Processor should give time to each of the
programs and process higher priority
processes first of all
- OS needs to keep all
programs separate
along with any data
they use
- Spooling
- Memory used to store data that has
been inputted by user or that is
about to be outputted until the
processor deals with it
- Memory used to store data that has
been inputted by user or that is
about to be outputted until the
processor deals with it
- Loader
- Remembers memory
locations of each
instruction or each piece of
data
- Remembers memory
locations of each
instruction or each piece of
data
- More than one program
should be stored in memory
and the processor should give
time to each of the programs
- An OS must:
- How Interrupts are Used to Obtain
Processor Time and how Processing
of Interrupted Jobs may Later be
Resumes
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