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OCR Computing A Level > Unit 2 Systems Software and Applications > Flashcards

Unit 2 Systems Software and Applications Flashcards

1
Q

What does the Operating System do?

A

Manages the hardware and provides an interface for the user and the application software

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2
Q

What functions does the OS provide? (4)

A
  • User interface
  • Memory management
  • Interrupt handling
  • Processor scheduling
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3
Q

What is Paging?

A

Available memory is divided into fixed chunks(pages). Each page has an address. Each running program in RAM is given sufficient pages but pages may not be contiguous

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4
Q

What is Segmentation?

A

Memory is divided into segments that can be different lengths. A particular function or subroutine occupies each segment

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5
Q

When does the CPU check for Interruptions?

A

After each clock cycle

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6
Q

How does a Stack work?

A

When an interrupt occurs, the processor stops fetching instructions and pushes its contents of its registers on a stack. First on, last off

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7
Q

What is a Round Robin?

A

Each job is given a fixed time slice and if its not completed in time the next job is allocated a time slice

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8
Q

What is First Come First Serve?

A

The first job to arrive is executed until it completes

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9
Q

What is Shortest Remaining Time?

A

Each has job an estimated completion time. The job with the shortest remaining time to completion is executed, meaning that a shorter new job can take over from the current process

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10
Q

What is Shortest Job Time?

A

Each job has a completion time estimated by the user. The job with the shortest completion time is executed when the current job completes

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11
Q

What is a Multi Level Feedback Queue?

A

Multiple queues are created with different priority levels. If a job uses too much CPU time it is moved to a lower priority queue. Processes can also be moved to a higher priority queue if they have waited a long time

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12
Q

What can Distributed Operating System do?

A

Coordinate the processing of a single job across multiple computers

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13
Q

What is BIOS?

A

Basic Input Output System
Boots the computer at start-up. Stored in ROM

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14
Q

What is a Device Driver?

A

A program that provides an interface for the OS to interact with a device. Drivers are hardware dependent and OS specific

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15
Q

What is a Virtual Machine?

A

A compute resource that uses software instead of a physical computer to run programs and deploy apps

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16
Q

What are the different types of System Software? (4)

A
  • Operating System
  • Utilities
  • Libraries
  • Translators
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17
Q

What functions do the OS provide? (4)

A
  • Provide a user interface
  • Handle memory management
  • Interrupt handling
  • Processor scheduling to provide ‘multi-tasking’
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18
Q

What does a Disk Defragmenter do?

A

Reorganizes the hard drive so that files are in sequential blocks where possible which makes reading quicker

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19
Q

What does Automatic Backup do?

A

Regularly backs up data in permanent storage

20
Q

What does Automatic Installing do?

A

Runs in the background detecting software update releases and automatically installing them

21
Q

What does Virus Checker do?

A

Scans permanent storage for viruses by comparing files to known virus definitions

22
Q

What does Compression Software do?

A

Reduces the size of files

23
Q

What are the categories of Application Software? (3)

A
  • General purpose
  • Special purpose
  • Bespoke
24
Q

What is the difference between Off-The-Shelf Software and Bespoke Software?

A

Off-the-shelf software is ready made software available for anyone to purchase. Bespoke software is custom made

25
Q

What is Open Source Software?

A

Software where anyone can access the source code, free to use and anyone may modify it. Different to freeware

26
Q

What is Freeware?

A

Software that is free to use but the source code is not available

27
Q

What is Closed Source (Proprietary) Software?

A

Software that does not allow access to the source code and users must pay to get a license to use it. There may be restrictions on how the software is used

28
Q

What criteria might you use when selecting an application to use? (5)

A
  • Functionality
  • Hardware
  • Cost
  • Availability
  • Reliability
29
Q

What is Assembly Code?

A

Instructions that are equivalent to machine code but easier for humans to work with

30
Q

What does an Assembler do?

A

Translates assembly code into machine code

31
Q

How does a Compiler work?

A

Translates a whole program written in a high level language into executable machine code, going through several stages

32
Q

How does an Interpreter work?

A

Translates code written in a high level language into machine code line by line

33
Q

What are the features of a Compiler? (4)

A
  • Programs can be run many times without needing compiling again
  • Faster to execute
  • Executable code does not require an interpreter to run
  • Compiled code can not be easily read and copied by others
34
Q

What are the features of an Interpreter? (2)

A
  • Source code can be run on any machine with an interpreter
  • If an error is found, code does not need to be fully compiled
35
Q

What is Bytecode?

A

An intermediate step between source code and machine code

36
Q

What are the 5 five stages of Compilation?

A

-Lexical analysis, Symbol table, Syntax analysis, Semantic analysis, Code generation

37
Q

What happens in Lexical Analysis?

A

All unnecessary spaces and all comments are removed. Keywords are replaced with tokens

38
Q

What happens in a Symbol Table?

A

The lexer will build up a symbol table for every keyword and identifier in the program
The symbol table helps to keep track of the run-time memory address for each identifier

39
Q

What happens in a Syntax Analysis?

A

The stream of tokens from the lexing stage is split up into phrases. Each phrase is parsed. If the phrase isn’t valid, an error will be recorded

40
Q

What does Parsing mean?

A

When a phrase is checked against the rules of the language

41
Q

What happens in Semantic Analysis?

A

The code is checked for errors that are logical not syntax

42
Q

What happens in Code Generation?

A

The compiler generates the machine code

43
Q

What happens in Code Optimisation

A

Redundant code is removed. Code is rewritten to be more efficient

44
Q

What is a Library?

A

Pre-written and pre-compiled functions. Can be written by a user and called within a program

45
Q

What does the Loader do?

A

Copies the program and any linked subroutines into main memory to run

OCR Computing A Level (13 decks)

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