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A-Level Computer Science > Functions Of An Operating System > Flashcards

Functions Of An Operating System Flashcards

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1
Q

What is an operating system?

A

A program or set of programs that manages that manages the operations of the computer to the user

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2
Q

Where is the operating system stored?

A

Permanent storage

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3
Q

What is the part of the operating system that is responsible for loading programs and libraries?

A

Loader

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4
Q

Where is the loader held?

A

ROM

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5
Q

What dies the operating system do when the computer is turned on?

A

The loader in the ROM sends the instruction to load the operating system by copying it from storage to RAM

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6
Q

What are the functions of the operating system?

A

User interface, memory management, interrupt service routines, processor scheduling, backing store management, input and output management

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7
Q

What will memory management do if the user wishes to switch from one application to another in a separate window?

A

Each application must be stored in memory simultaneously

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8
Q

What does paging and segmentation do?

A

Making the optimum use of memory by splitting it into small section

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9
Q

What does a paging system do?

A

Divides memory into fixed size pages of 4Kb each and a process currently in memory may be held in several non-contiguous pages

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10
Q

What is segmentation?

A

The logical division of address space into varying length segments which depend on the program structure

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11
Q

What is virtual memory?

A

Using secondary storage as an extension of memory to make room for the next job which has a share of the processor time

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12
Q

If more virtual memory is used what happens to performance?

A

Performance deaerates

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13
Q

What is an interrupt?

A

A signal from a software program, hardware device or internal clock to the CPU

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14
Q

When does a software interrupt occur?

A

When an application program terminates or request certain services for the operating system

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15
Q

When does a hardware interrupt occur?

A

When an I/O operation occurs or an error like ‘the printer is out of paper’ occurs

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16
Q

Why are interrupts also triggered by a timer?

A

To indicate that it is the turn of the next process to have processor time

17
Q

How is multi-tasking possible?

A

Because a processor can be interrupted

18
Q

When is an interrupt service routine used?

A

When the CPU receives an interrupt signal, suspending execution of the running program or process and disables all interrupts of a lower priority

19
Q

What is meant by processor scheduling?

A

The role the operating system plays by allocating processor time to each one as they compete for the CPU

20
Q

What is meant by multi-tasking?

A

Carrying out smaller parts of multiple larger tasks in turn, the processor can give the appearance of carrying out several tasks simultaneously

21
Q

What is the scheduler?

A

The operating system module responsible for making sure that processor time is used as efficiently as possible

22
Q

What are the objectives of the scheduler?

A

Maximise throughput, be fair to all users on a multi-user system, provide acceptable response time to all users and ensure hardware resources are kept as busy as possible

23
Q

What are the different scheduling algorithms?

A

Round robin, first come first served, shortest remaining time, shortest job first, multi-level feedback queue

24
Q

How does round robin scheduling work?

A

Processes are despatched on a first in first out (FIFO) basis, with each process in turn being given a limited amount of CPU time called a time slice or quantum and if the process does not complete before it time expires or before a higher priorty interrupt occurs, the despatcher gives the CPU to the next process

25
Q

How does first come first served work?

A

Jobs are processed in the order in which they arrive, with no system of priotires

26
Q

in round robin how does the scheduling generate interrupts at specific times?

A

The operating system sets an interrupting clock or interval timer

27
Q

What does a round robin scheduling help guarantee?

A

Guarantee a reasonable response time to all users of the system

28
Q

How does shortest remaining time scheduling work?

A

The smallest estimate time to completion is run next

29
Q

What does shortest remaining time scheduling do?

A

Reduces the number of waiting jobs, and the number of small jobs waiting behind big jobs

30
Q

What is a disadvantage of shortest remaining time scheduling?

A

requires knowledge of how long a job will take, so the user has to estimate the job time

31
Q

How does shortest job first scheduling work?

A

The process of smallest estimated running time is run next

32
Q

what is multi-level feedback queues scheduling designed to?

A

Give preference to short jobs, give preference to I/O bound processes and separates processes into categories based on their need for the processor

33
Q

How does multi-level feedback queues scheduling work?

A

The algorithm implements several job queues and job can move between queues, depending on how much processor time they use

34
Q

What is the aim of multi-level feedback queues scheduling?

A

Maximise processor use

35
Q

What is the operating system required to store to know where files are stored so they can be quickly accessed?

A

A directory of files

36
Q

What system, that comes with you desktop operating system, enables a user to moves files and folders, delete files and protect others from unauthorised access?

A

File management system

37
Q

What is a buffer?

A

The data to be sent to an input or output device will then be transferred to an area of memory, so that the CPU can continue with another task

38
Q

What is peripheral management?

A

The operating system needing to communicate with input or output systems which their are a lot of different types of

39
Q

What is the purpose of a buffer?

A

To compensate for the difference in speed between the output device and the CPU

A-Level Computer Science (20 decks)

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