1.2.2 Application Software

Question 1

What is application software?

Answer 1

• 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.

Question 2

What are some examples of application software?

Answer 2

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

Question 3

What is Systems software?

Answer 3

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

Question 4

What are some examples of systems software?

Answer 4

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

Question 5

What are utilities?

Answer 5

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.

Question 6

What are some examples of utility software?

Answer 6

Compression, disk defragmentation, automatic updating, backup

Question 7

What is source code?

Answer 7

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

Question 8

What is the definition of open source software?

Answer 8

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

Question 9

What is closed source software?

Answer 9

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

Question 10

What are advantages of open source software?

Answer 10

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

Question 11

What are advantages of closed source software?

Answer 11

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

Question 12

What are disadvantages of open source software?

Answer 12

• Support available online may be insufficient or incorrect. No user manuals.
• Lower security as may not be developed in a controlled environment
• Difficult to monetise

Question 13

What are disadvantages of closed source software?

Answer 13

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

Question 14

What are translators?

Answer 14

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.

Question 15

What are the three types of translators?

Answer 15

• Compiler
• Interpreter
• Assembler

Question 16

What are compilers?

Answer 16

• 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

Question 17

What are interpreters?

Answer 17

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

Question 18

What is assembely code?

Answer 18

• Assembly code is considered to be a low-level languageas it is the ‘next level up’ from machine code.
• It is platform specific

Question 19

What are assemblers?

Answer 19

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

Question 20

What are the stages of compilation?

Answer 20

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

Question 21

What happens in lexical analysis?

Answer 21

• 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.

Question 22

What happens in syntax analysis?

Answer 22

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

Question 23

What happens in code generation?

Answer 23

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

Question 24

What happens in optimisation?

Answer 24

• 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

Question 25

What are libraries?

Answer 25

* 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

Question 26

What are linkers?

Answer 26

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

Question 27

How do Static Linkers work?

Answer 27

* Module/library is added directly to main file * Increases size of file * External updates wont affect program

Question 28

How do Dynamic Linkers work?

Answer 28

* 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.

Question 29

What are loaders?

Answer 29

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

Question 30

What is bytecode?

Answer 30

* Platform independent compiled code * Executed by a bytecode interpreter on client