Computer science

What is Paging

Memory split into equal-sized sections known as pages.
They're swapped between main memory and the hard disk as needed.

What is Segmentation

Memory split into logical sized divisions, called segments.
● They vary in size as they are split logically

What does an OS do?

○ Memory management
○ Resource management eg. scheduling
○ File management
○ Input/ Output management
○ Interrupt management
○ Utility software
○ Security
○ User interface

Stages of Compilation

Lexical Analysis
Syntax analysis
Code generation
Optimization

Steps of Lexical Analysis

White space and comments are removed
Keywords and Names of variables are replaced with tokens and are stored in a symbol table

Steps of syntax analysis

Tokens are analysed for errors (flagged as errors)
Semantic analysis: logic mistakes in program are detected
Abstract syntax tree is produced

Code Generation

Abstract syntax tree is used to produce machine code

Optimisation

Make code more efficient
Redundant parts of coded removed
Repeated sections of code code are replaced with more efficient code

First come first serve

Exectuted in order they arrive

Round Robin

Given a fixed quantum to complete task and if not completed returned to back of queue

Shortest remaining

Queue sorted by shortest completion time - processes that arrive that have a shorter processing time than current running one is swapped

Shortest Job First

Sorted by estimated completion time