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A-level computer science > 1.2.1 Systems Software > Flashcards

1.2.1 Systems Software Flashcards

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1
Q

What is application software?

A
  • Applications software is designed to be used by the end-user to perform one specific task.
  • Application software requires systems software in order to run.
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2
Q

What are some examples of application software?

A

Examples: desktop publishing, word processing, spreadsheets, web browsers

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3
Q

What is Systems software?

A

Systems software is low-level software that is responsible for running the computer system
smoothly, interacting with hardware and generally providing a platform for applications
software to run.

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4
Q

What are some examples of systems software?

A

Examples: library programs, utility programs, operating system, device drivers.

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5
Q

What are utilities?

A

Systems software designed to ensure the consisted,high performance of the OS. Each utility program has a specific function linked to maintenance of the OS.

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6
Q

What are some examples of systems software?

A

Compression, disk defragmentation, automatic updating, backup

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7
Q

What is source code?

A

Written by a programmer and refers to object code before it has been compiled.

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8
Q

What is the definition of open source software?

A

Open source software can be usedby anyone without a license and is distributed with the source code.

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9
Q

What is closed source software?

A

Closed source software requires the user to hold an appropriate
license to use it. Users cannot access the source code as the
company owns the copyright license.

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10
Q

What are advantages of open source software?

A
  • Can be modified and improved by anyone
  • Technical support from online community
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11
Q

What are advantages of closed source software?

A
  • Thorough, regular and well-tested updates
  • Company owning software provides expert support and user
    manuals.
  • High levels of security as developed professionally.
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12
Q

What are disadvantages of open source software?

A
  • Support available online may be insufficient or incorrect. No user manuals.
  • Lower security as may not be developed in a controlled environment
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13
Q

What are disadvantages of closed source software?

A
  • License restricts how many people can use the software at once
  • Users cannot modify and improve software themselves
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14
Q

What are translators?

A

A translator is a program that converts high-level source
code into low-level object code, which is then ready to be
executed by a computer.

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15
Q

What are the three types of translators?

A
  • Compiler
  • Interpreter
  • Assembler
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16
Q

What are compilers?

A
  • Complilers translate high-level code into machine code all at once after checking that the code is error-free.
  • After compilation, an .exe file is produced which can be execute without needed to complie again.
  • Will not compile if there is an error.
  • Initial compilation is longer than interpreter of assembler
17
Q

What are interpreters?

A
  • Interpreters translate and execute code line-by-line.
  • Code must be interpreted every time it is run
  • Not all code may be run (selection)
18
Q

What is assembely code?

A
  • Assembly code is considered to be a low-level language
    as it is the ‘next level up’ from machine code.
  • It is platform specific
19
Q

What are assemblers?

A
  • Assemblers translate assembly code into machine code
  • One lien of assembely code is almost equivilent to one line of machine code
20
Q

What are the stages of compilation?

A

Lingering,Side-effects,Consuming,Opium
* Lexical Analysis
* Syntax analysis
* Code generation
* Optimisation

21
Q

What happens in lexical analysis?

A
  • Whitespace and comments are removed from the code.
  • The remaining code is analysed for keywords and names of variables and constants.
  • These are replaced with tokens and information about the token associated with each keyword or identifier is stored in a symbol table.
22
Q

What happens in syntax analysis?

A
  • Code (now tokenised) is checked against the rules and grammar of the programming language aka “Parsinh”:applying set of rules to each statement to check if it is valif
  • Errors are reported as a list
  • Details of data types are added to symbol table
  • Abstract syntax tree produced
23
Q

What happens in code generation?

A
  • The abstract syntax tree produced in the syntax analysis stage is used to produce machine code.
24
Q

What happens in optimisation?

A
  • Searches for ways to reduce the runtime of the code(make it more efficient)
  • Can add significant amount of time taken to overall compilation.
  • Removes insignificant parts of code.
  • Repeated sections may be replaced with more efficient peice of code
  • However, it may sometimes result in nunexpected results
25
Q

What are libraries?

A
  • Pre-compiled programs which can be incorporated within other programs.
  • Error-free
  • Save time and effort of developing and testing modules
  • Can be reused across multiple programs
26
Q

What are linkers?

A

Software that is responsible for linking external modules and libraries included within the code. There are two types of linker:
* Static Linker
* Dynamic Linker

27
Q

How do Static Linkers work?

A
  • Module/library is added directly to main file
  • Increases size of file
  • External updates wont affect program
28
Q

How do Dynamic Linkers work?

A
  • Addresses of modules and libraries are included in the file where they are referenced.
  • When program is run, the loader retrieves the program at the address
  • External updates feed through to the main file; there is no need to rewrite the code.
29
Q

What are loaders?

A
  • Programs provides by the OS
  • When a file is executed, the loader retrieves the library or subroutine from the given memory location.
30
Q

What is bytecode?

A
  • Platform independent compiled code
  • Executed by a bytecode interpreter on client

A-level computer science (6 decks)

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