1.2.2 - Applications Generation

Question 1

Types of software

Answer 1

Systems software
Applications software

Question 2

System software purpose

Answer 2

To control hardware and run applications

Question 3

Examples of systems software

Answer 3

Operating system
Utility software
Libraries
Translators

Question 4

Types of application software

Answer 4

General purpose
Special purpose
Bespoke software

Question 5

Bespoke software

Answer 5

Custom created for a specific user and mostly used by businesses rather than individuals

Question 6

Open source software

Answer 6

Anyone can access the source code
Licensed but free to use
Anyone can modify the software and sell it as long as the product is also open source

Question 7

Freeqare

Answer 7

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

Question 8

Proprietary software

Answer 8

No access to source code
Users must pay copyright owner for license to use
May be restrictions on use depending on license

Question 9

Factors affecting choice of applications

Answer 9

Functionality
Hardware compatibility
Availability
Cost
Reliability
Reputation

Question 10

Assembler

Answer 10

Translates assembly language into machine code
Hardware specific

Question 11

Compiler

Answer 11

Translates a whole program written in high level language into machine code

Question 12

Interpreter

Answer 12

Translates program line by line into machine code

Question 13

Positives of compilers

Answer 13

Program can be run many times without the need to recompile
Faster to execute
Executable code does not require an interpreter to run
Compiled code cannot be easily read and copied by others

Question 14

Positives of interpreters

Answer 14

Source code can be run on any machine with the interpreter
If a small error is found, no need to recompile the entire program

Question 15

Bytecode

Answer 15

Intermediary step between source code and machine code, this is then interpreted by a bytecode interpreter

Question 16

Stages of compilation

Answer 16

Lexical analysis
Syntax analysis
Semantic analysis
Code generation

Question 17

Lexical analysis

Answer 17

Whitespace and comments removed
Keywords, contents and identifiers replaced with tokens
Lexer will build a symbol table for run-time memory addresses of identifiers

Question 18

Syntax analysis

Answer 18

Stream of tokens split into phrases
Phrases are parsed against the rules of the language
Error recorded if phrase is not valid
Syntax rules can be drawn as a syntax diagram

Question 19

Semantic analysis

Answer 19

Checks for valid syntax that is not a valid program

Question 20

Code generation

Answer 20

Compiler generates machine code
Code optimisation is also performed

Question 21

Code optimisation

Answer 21

Removes redundant instructions
Replaces inefficient code with more efficient code

Question 22

Libraries

Answer 22

Pre-written and pre-compiled functions
Programmers can write their own libraries

Question 23

Linker

Answer 23

Puts appropriate memory addresses in place so that the program can call and return from a library function

Question 24

Loader

Answer 24

Copies program and any linked subroutines into main memory to run