SYSTEMS SOFTWARE Flashcards

1
Q

What is an operating system

A

Software that controls the computer, manages the computer’s hardware and the programs running on it

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2
Q

Examples of OS

A

Windows, MacOS, Linux, IOS and Android

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3
Q

Roles of an operating systems

A
  • Manage the system hardware
  • Manage the installation and running of programs
  • Manage the security of the system
  • Provide a user interface
  • Memory management
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4
Q

What is paging

A

Programs are physically divided into equal-sized blocks called pages

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5
Q

What is segmentation

A

Programs are logically divided into unequal blocks containing modules or routines

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6
Q

What is virtual memory

A

The use of secondary storage as an extension of a computer’s physical memory

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7
Q

What is disk thrashing

A

When pages are being swapped from main memory to virtual memory too often, slowing down the computer

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8
Q

What is an interrupt

A

A signal sent to a CPU to signify another processor is in need of processing time

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9
Q

What is the ISR

A

Interrupt Service Routine - This is the program code that is called when an interrupt is triggered

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10
Q

What happens when an interrupt occurs

A
  • The contents of the PC and other registers are copied to an area of memory called a stack
  • The ISR can be loaded by changing the PC to the location of the ISR in memory
  • When the ISR is completed the previous content is restored from the stack to the CPU
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11
Q

What happens when an interrupt is being serviced, a higher priority interrupt occurs

A

The interrupt will be added to the stack and the new interrupt is serviced. After, the previous interrupt is taken off the stack and continued

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12
Q

What is scheduling

A

The method an OS uses to ensure all processes get sufficient processor time

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13
Q

Describe the round robin algorithm

A

Each process is given a fixed amount of time. If it hasn’t finished by the end of that time period, it goes to the back of the queue so the next process in line can have its turn

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14
Q

Describe the first come first served algorithm

A

The first process to arrive is dealt with by the CPU until it’s finished. Any other processes that come along are queued up waiting for their turn

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15
Q

Describe the shortest job first algorithm

A

Picks the job that will take the shortest time and run it until it finishes

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16
Q

Describe the shortest remaining time algorithm

A

The scheduler estimates how long each process will take. It then runs the one that will take the least amount of time. If a process hasn’t completed after a certain amount of time, the scheduler checks to see whether any shorter process have been added

17
Q

Describe the multilevel feedback queues algorithm

A

Uses multiple queues. Each of these queues has a different priority. The algorithm can move jobs between these queues depending on the jobs behaviour

18
Q

Describe distributed OS and an example where it is used

A

Allows multiple computers to work together on a single task. They tend to be used in systems aimed at completing computationally intensive tasks.
e.g 3D animation

19
Q

What are embedded systems and an example of one

A

A dedicated computer system that performs one or more specific functions within a larger piece of equipment.
e.g, washing machines, vending machines

20
Q

Describe multitasking OS

A

Can run multiple programs simultaneously

21
Q

Describe multi-user OS and an example where it is used

A

Allows multiple users to use a system and its resources simultaneously.
e.g Banks and retailers

22
Q

Describe real-time OS and an example where it is used

A

Designed to carry out actions within a guaranteed amount of time even when left running on long periods. Usually the expected response time is within a small fraction of a second
e.g autopilot

23
Q

What is the BIOS

A

Basic Input/Output System - The program a computer’s microprocessor uses to start the computer system after it is powered on

24
Q

What is a device driver

A

A piece of software that tells the computer how it can communicate with hardware

25
Q

What is a virtual machine

A

A program that has the same functionality as a physical machine

26
Q

Uses of virtual machines

A
  • Run one OS within another OS
    - a program needed that can’t run on the host OS
    - offers a convenient way to test a program being developed on multiple platforms
  • Interpreting intermediate code