SLR 04 - Operating Systems & System Software

Question 1

What does the OS handle?

Answer 1

User Access / Logging in
Application Software
Memory Management
User Interface
Utility Programs
File Management
Device Drivers

Question 2

What is Multitasking?

Answer 2

The processor allocating time to several processes when multiple apps are open

Question 3

What is defragmentation?

Answer 3

When there is space for a program but not contigually, it moves programs to make space for a program to be in RAM

Question 4

What is Paging?

Answer 4

Pages are of a fixed size
Made up of physical divisions
Programs are split up into a series of pages
Can be inefficient as programs in a loop can be spread in RAM

Question 5

What is Segmentation?

Answer 5

Segments are different sizes
They are complete sections of programs
Segments are logical divides

Question 6

What are the similarities between Segments and Pages?

Answer 6

Both run despite insufficient memory
Both are stored on disks
They are transferred onto memory when needed

Question 7

What are the differences between Segments and Pages?

Answer 7

Pages are fixed sizes, segments are different
Pages fit memory, segments have program sections
Pages are physical, Segments are logical

Question 8

What is virtual memory?

Answer 8

When physical memory is running low virtual memory is used
If more time is used moving data in memory than processing it, the computer is slowed

Question 9

When do interrupts occur in the FDE cycle?

Answer 9

After execute

Question 10

What are interrupts?

Answer 10

A way to signal the processor from other devices during the FDE

Question 11

What does ISR stand for?

Answer 11

The Interrupt Service Routine

Question 12

What occurs during the ISR?

Answer 12

The contents of the interrupt register is copied to the program counter for the instruction of the interrupt
Registers contents from before the interrupt are copied into a stack for retrieval
Once the interrupt is complete these are copied back into the registers continuing the program from before the interrupt

Question 13

What are some examples of interrupts?

Answer 13

Power Down : Hardware
Moving the mouse : User
Arithmetic Overflow : Software
Screen Recording app : Timer
Buffer Empty : Input / Output

Question 14

What do schedulers allow for?

Answer 14

Effective management of multi-tasking operating systems

Question 15

What do schedulers manage?

Answer 15

What to process next
The length of time a process can execute for

Question 16

What are examples of sceduling algorithms?

Answer 16

FCFS - First come first serve
SJF - Shortest job first
RR - Round Robin
SRT - Shortest remaining time
MLFQ - Multi-Level feedback queue

Question 17

How does FCFS work?

Answer 17

Processes execute in the order they arrive
Processes waiting in queue just wait

Question 18

How does SJF work?

Answer 18

Picks processes that take the least time and run til completion
Follows same post-execute process as FCFS

Question 19

How does RR work?

Answer 19

Each process is alocated a time slice
If not completed by the end of this it returns to the back of the ready queue

Question 20

How does SRT work?

Answer 20

Similar to SJF
Processes are suspended if higher-priority processes join the queue

Question 21

How does MLFQ work?

Answer 21

Used in multi-processor systems
Can handle multiple process queues at the same time
Scheduler moves jobs between queues as needed

Question 22

What is a device driver?

Answer 22

It is software that translated code to be understood by another device

Question 23

What are the types of operating systems?

Answer 23

Distributed
Multi-Tasking
Multi-User
Embedded
Real-Time

Question 24

What is distributed computing?

Answer 24

When the OS controls and co-ordinated several computers and presents them as 1 system

Question 25

What is an embedded OS?

Answer 25

It runs on dedicated hardware to maximise efficiency of a system using little memory

Question 26

What is a real-time OS?

Answer 26

Processes in real-time systems must execute in a certain time frame
Redundancy is built into real-time systems to handle sudden increases in input
Real-time systems rarely run at full capacity