Systems Software

Question 1

Purposes of OS

Answer 1

Managing processor, managing memory, managing external devices, platform for software and utility programs, provides networking, managing security, user interface, interrupt service routine, backing store management

Question 2

Paging

Answer 2

Program divided into equal sized sections

Code loop could be separated

Question 3

Segmentation

Answer 3

Logical divisions of program by functions and based on contents

Question 4

Scheduling algorithms

Answer 4

1st come 1st serve
Shortest job 1st
Round robin (each process given time slice and if not finished in time, to back of queue)
Shortest remaining time

Question 5

Types of OS

Answer 5

Multi tasking 
Multi user
Distributed 
Embedded
Real time

Question 6

Utility (def)

Answer 6

Maintenance software

Optimise performance of computer

Question 7

Utility (types)

Answer 7

Disk defragmenter (reorganise hard disk so files are in contiguous order)
Automatic Backup
Automatic Updating
Virus checking
Compression software

Question 8

Scheduling (def)

Answer 8

Ensure all jobs are processed and as many as possible

Utilise time and resources efficiently

Question 9

Interrupt

Answer 9

A signal to the processor indicating a device or process needs attention

Question 10

ISR

Answer 10

When interrupt sent out, if lower/equal priority to current process, then process continues

If not, CPU finishes current fetch, decode etc cycle
Content of CPU register copied to stack in memory
Location of ISR loaded into program counter
When ISR complete, previous content popped from stack back to register

Question 11

Assembler

Answer 11

Source code/ assembly / low level to machine / object code

Question 12

Compiler

Answer 12

All at once
Specific to hardware
Harder to reverse engineer
Portable

Question 13

Interpreter

Answer 13

Each line translated individually
Platform independent
Good for program development

Question 14

Bytevode

Answer 14

Combination

Java Virtual Machine corrects bytecode to machine code

Question 15

Stages of compilation

Answer 15

Lexical analysis (white space, comments removed, keywords etc to tokens)
Syntax analysis and semantic analysis (check if tokens are following rules of language, add data types to table ) 
Code generation and optimisation (reduce execution time, remove redundant instructions, give variables in table physical addresses, make object code )

Question 16

Linkers and loaders

Answer 16

Connect separately compiled subroutines / libraries