1.2.1 Operating System

Question 1

What does BIOS stand for?

Answer 1

Basic input output system

Question 2

What is the BIOS?

Answer 2

A program that initialises and tests whether system hardware is functional and then loads the operating system from the hard disk into RAM

Question 3

What are device drivers?

Answer 3

A program supplied with a peripheral device that allows the OS to control and communicate with the device

Question 4

What are distributed operating systems?

Answer 4

This is a type of operating system that is run across multiple devices, allowing the load to be spread across multiple computer processors when a task is run.

Question 5

What is an embedded operating system?

Answer 5

Built to perform a small range of specific tasks, this operating system is catered towards a specific device.
They are limited in their functionality and hard to update although they consume significantly less power than other types of OS.

Question 6

What is intermediate code?

Answer 6

Code partly translated between high-level and machine language produced by a computer

Question 7

What are interupts?

Answer 7

A signal from hardware, software or the clock to alert the CPU.
If the interrupt is a higher priority than the current task the current routine pauses and resumes after the interrupt is executed.

Question 8

What are interrupt service routines (ISR)?

Answer 8

If an interrupt is a higher priority than the current task, register contents are temporarily transferred onto the system stack at the end of the current FDE cycle and the interrupt is handled.

Question 9

What is memory management?

Answer 9

The efficient organisation and allocation of main memory to the programs in use

Question 10

What are multi-level feedback queues?

Answer 10

A scheduling algorithm that uses multiple queues, each with a different priority. Jobs can be moved between queues

Question 11

What are multi-tasking operating systems?

Answer 11

Multi-tasking operating systems enable the user to carry out tasks seemingly simultaneously.
This is done by using time slicing to switch quickly between programs and applications in memory.

Question 12

What are multi-user operating systems?

Answer 12

An operating system consisting of one mainframe computer with multiple terminals that allow multiple users to access the computers resources.
Each user is given a time slice of the mainframe processor.

Question 13

What is the operating system?

Answer 13

A set of programs managing the operation of the computer that is loaded into RAM every time the computer is turned on.
It bridges the user to the hardware.

Question 14

What are real-time operating systems?

Answer 14

An operating system where data is processed as it comes, with response generated with a guaranteed timeframe.
Commonly used in time-critical computer systems.

Question 15

What is a virtual machine?

Answer 15

Any instance where software is used to take on the function of a machine, including intermediate code or running an operating system within another.

Question 16

What is paging?

Answer 16

Paging is when memory is split into equal-sized sections known as pages, with programs comprising a certain number of equally-sized pages.
These can then be swapped between the main memory and the hard disk.

Question 17

What is scheduling?

Answer 17

Allocating processor time to each application to ensure processor time us used as efficiently as possible when multitasking

Question 18

What is segmentation?

Answer 18

Segmentation is the splitting up of memory into logical-sized divisions, known as segments, which vary in size.
These represent the program’s structure and logical flow, with segments allocated to blocks of code such as conditional statements or loops.

Question 19

What is virtual memory?

Answer 19

Virtual memory uses a section of the hard drive to act as RAM when the space in main memory is insufficient to store programs being used.
Sections of programs that are not currently in use are temporarily moved into virtual memory through paging, freeing up memory for other programs in RAM.

Question 20

What eight things does the operating system do?

Answer 20

Memory management
Resource management
File management
Input/output management
Interrupt management
Utility software
Security
User interface

Question 21

Describe Round robin scheduling

Answer 21

Each job is given a section of processor time - known as a time slice - within which it is allowed to execute.
Once each job in the queue has used its first time slice, the operating system again grants each job an equal slice of processor time.
Once a job has been completed it is removed from the queue.

Question 22

What are two negatives about round robin scheduling?

Answer 22

Although Round Robin ensures each job is seen, longer jobs will take a much longer time for completion due to their execution being inefficiently split up into multiple cycles.
This algorithm also does not take into account job priority.

Question 22

Describe First come first served scheduling

Answer 22

Jobs are processed in chronological order by which they entered the queue. Although this is straightforward to implement.

Question 23

What is a negative about first come first served?

Answer 23

FCFS again does not allocate processor time based on priority.

Question 24

What is a negative about multilevel feedback queues?

Answer 24

Can be difficult to implement due to deciding which job to prioritise based on a combination of priorities.

Question 25

Describe shortest job first scheduling

Answer 25

The queue storing jobs to be processed is ordered according to the time required for completion, with the longest jobs being serviced at the end.
This type of scheduling is most suited to batch systems, where shorter jobs are given preference to minimise waiting time.

Question 26

What are two negatives of shortest job first scheduling?

Answer 26

It requires the processor to know or calculate how long each job will take and this is not always possible. There is also a risk of processor starvation if short jobs continue being added to the job queue.

Question 27

What is processor starvation?

Answer 27

When a particular process does not recieve enough processor time in order to execute and be completed.

Question 28

What is the POST?

Answer 28

POST (Power-on self test) which ensures that all hardware (keyboards, disk drives) are correctly connected and functional

Question 29

What are 2 uses of virtual machines?

Answer 29

Protection from malware: Malware will affect the virtual machine rather than the device being used.
Running incompatible software: Programs specific to different operating systems or different versions of an operating system can be run within a VM, saving the time and money required to purchase the hardware.