16.01 - Purposes of an Operating System (OS)

Question 1

Bootstrap

Answer 1

A small program that is used to load other programs to “start up” a computer

Question 2

Scheduling

Answer 2

Process manager which handles the removal of running programs from the CPU and the selection of new processes

Question 3

Direct memory access (DMA) controller

Answer 3

Device that allows certain hardware to access RAM independently of the CPU

Question 4

Kernel

Answer 4

The core of an OS with control over process management, memory management, interrupt handling, device management, and I/O operations

Question 5

Multi-tasking

Answer 5

Function allowing a computer to process more than one task/process at a time

Question 6

Process

Answer 6

A program that has started to be executed

Question 7

Pre-emptive

Answer 7

Type of scheduling in which a process switches from running state to steady state or from waiting state to steady state

Question 8

Quantum

Answer 8

A fixed time slice allocated to a process

Question 9

Non-preemptive

Answer 9

Type of scheduling in which a process terminates or switches from a running state to a waiting state

Question 10

Burst time

Answer 10

The time when a process has control of the CPU

Question 11

Starve

Answer 11

To constantly deprive a process of the necessary resources to carry out a task/process

Question 12

Low-level scheduling

Answer 12

Method by which a system assigns a processor to a task or process based on the priority level

Question 13

Process control block (PCB)

Answer 13

Data structure which contains all the data needed for a process to run

Question 14

Process states

Answer 14

Running, ready, and blocked; the states of a process requiring execution

Question 15

Round robin (scheduling)

Answer 15

Scheduling algorithm that uses time slices assigned to each process in a job queue

Question 16

Context switching

Answer 16

Procedure by which, when the next process takes control of the CPU, its previous state is reinstated or restored

Question 17

Interrupt dispatch table (IDT)

Answer 17

Data structure used to implement an interrupt vector table

Question 18

Interrupt priority levels (IPL)

Answer 18

Values given to interrupts based on values 0 to 31

Question 19

Optimisation (memory management)

Answer 19

Function of memory management deciding which processes should be in main memory and where they should be stored

Question 20

Paging

Answer 20

Form of memory management which divides up physical memory and logical memory into fixed-size memory blocks

Question 21

Physical memory

Answer 21

Main/primary RAM memory

Question 22

Logical memory

Answer 22

The address space that an OS perceives to be main storage

Question 23

Frames

Answer 23

Fixed-size physical memory blocks

Question 24

Pages

Answer 24

Fixed-size logical memory blocks

Question 25

Page table

Answer 25

Table that maps logical addresses to physical addresses; it contains page number, flag status, frame address, and time of entry

Question 26

Dirty

Answer 26

Term used to describe a page in memory that has been modified

Question 27

Translation lookaside buffer (TLB)

Answer 27

This is a memory cache which can reduce the time taken to access a user memory location; it is part of the memory management unit

Question 28

Segments memory

Answer 28

Variable-size memory blocks into which logical memory is split up

Question 29

Segment number

Answer 29

Index number of a segment

Question 30

Segment map table

Answer 30

Table containing the segment number, segment size, and corresponding memory location in physical memory: it maps logical memory segments to physical memory

Question 31

Virtual memory

Answer 31

Type of paging that gives the illusion of unlimited memory being available

Question 32

Swap space

Answer 32

Space on HDD used in virtual memory, which saves process data

Question 33

In demand paging

Answer 33

A form of data swapping where pages of data are not copied from HDD/SSD into RAM until they are actually required

Question 34

Disk thrashing

Answer 34

Problem resulting from use of virtual memory. Excessive swapping in and out of virtual memory leads to a high rate of hard disk read/write movements, thus reducing processing speed

Question 35

Thrash point

Answer 35

Point at which the execution of a process comes to a halt since the system is busier paging in/out of memory rather than actually executing them

Question 36

Page replacement

Answer 36

Occurs when a requested page is not in memory and a free page cannot be used to satisfy allocation

Question 37

Page fault

Answer 37

Occurs when a new page is referred but is not yet in memory

Question 38

First in first out (FIFO) page replacement

Answer 38

Page replacement that keeps track of all pages in memory using a queue structure. The oldest page is at the front of the queue and is the first to be removed when a new page is added

Question 39

Belady's anomaly

Answer 39

Phenomenon which means it is possible to have more page faults when increasing the number of page frames

Question 40

Optimal page replacement

Answer 40

Page replacement algorithm that looks forward in time to see which frame to replace in the event of a page fault

Question 41

Least recently used (LRU) page replacement

Answer 41

Page replacement algorithm in which the page which has not been used for the longest time is replaced