1.2.2 Applications Generation

Question 1

Describe and give examples of applications software

Answer 1

Performs generic tasks for the user.

Examples:
- Database (DBMS)
- Word processor
- Spreadsheet
- Graphics editor
- Desktop Publisher (DTP)

Question 2

Describe and give examples of utility software

Answer 2

A program with one specific purpose

A piece of system software used for the maintenance of the system

Examples:
- Disk Defragmenter
- Compression Utility
- Anti-Virus/Malware
- Device driver
- Firewall

Question 3

Describe open-source software

Answer 3

Source code is freely available for others to amend / recompile

Can be built on to tailor the program to specific needs without starting from scratch

Code open for bugs to be spotted and fixed.

Has the benefit of a community potentially improving the system

Question 4

Describe closed-source software (propriety)

Answer 4

The source code is not made available

Distributed in binary form

There is no permission to amend the program code, so cannot be ‘tweaked’

Users are sold a license to use it (with conditions).

Question 5

Describe and give examples of software libraries

Answer 5

Pre-written blocks of code that contain useful routines that can be imported into a program.

Examples: encryption and graphic routines

Question 6

What are the benefits of libraries?

Answer 6

Relatively error-free as has already been tested by the author

Already written so are ready to use which saves time/money

Used multiple times for common tasks which reduces repeated code

The programmer can use code beyond their expertise

Written by an expert so should be efficient

Different source languages can be used to increase features

Question 7

What are the negatives of using software libraries?

Answer 7

May significantly increase the size of the compiled file as the library contains many routines that aren’t being used.

Not written by the programmer so need to spend time familiarising themselves with it.

Question 8

Describe machine code

Answer 8

The output of a translator

Uses binary notation (0101010101000011)

Dependent on architecture

Harder to program

Question 9

Describe high-level languages

Answer 9

Not architecture specific

Can be recompiled for different architectures.

Close to English

Question 10

Describe assembly language

Answer 10

Uses mnemonics to represent machine code instructions/opcodes

Consists of simple instructions

Specific to the instruction set of the given processor

Question 11

What is a translator?

Answer 11

Software that converts code from high-level, or assembly, to machine code

Question 12

What are the 3 types of translators?

Answer 12

Interpreter

Compiler

Assembler

Question 13

Describe an interpreter and give an example of a language that would use one.

Answer 13

Translates source code every time the program is run

The user needs access to the source code to run the program

Will run on any machine

The slowest option for translators

Translates code line by line

Example: JavaScript

Question 14

Describe a compiler and give an example of a language that would use one.

Answer 14

Machine dependent - different compilers are needed for each type of machine

Creates an executable program (.exe)

Users do not see the source code

Will run quicker than the other options.

Translates all the high-level code at once

Example: C#

Question 15

Describe an assembler and give an example of a language that would use one.

Answer 15

Used to convert assembly language into machine code

Replaces mnemonic opcodes with machine codes

Replaces symbolic addresses with numeric addresses

Creates one line of object code for each line of source code.

Example Assembly Language

Question 16

State the stages of compilation

Answer 16

Lexical Analysis

Syntax Analysis

Code Generation

Optimisation

Question 17

Describe the lexical analysis stage

Answer 17

Comments and whitespace are removed

The symbol table is started

Variable names like ‘count’ are added to a symbol table.

Reserved words like ‘WHILE’ are tokenized.

The series of tokens and symbol table is passed onto the next stage, syntax analysis

Question 18

Describe the syntax analysis stage

Answer 18

Receives output from the lexical analysis

Code is checked to ensure it follows the rules of the language

Uses abstract syntax trees to check syntax rules are followed.

The symbol table is completed

An error list is generated at the end of this stage

Question 19

Describe the code generation stage

Answer 19

Receives the abstract syntax trees from syntax analysis

The object code is created (machine code)

Turns the code into a format that the processor can understand

Question 20

Describe code optimisation

Answer 20

Ensures the code runs quicker and uses less memory.

The code from the prior stages may have been inefficient (instructions used that can be replaced by simpler ones.)

Question 21

Describe the purpose and types of linker

Answer 21

At the end of compilation, a linker is used to combine the object code with the library code to make the single executable file

Links the main program to libraries

can either include them in the final executable code (static)
…or get the executable code to point to the external libraries (dynamic)

Question 22

Describe the purpose of a loader

Answer 22

A program in an operating system (OS) used to load the executable file (exe)

Loads the required libraries

Allocates the memory space to the executable module in the main memory.