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)
- Presentation Software
- Computer Aided Design (CAD)

Question 2

Which category of software would be used to perform each of the following tasks?

Answer 2

Question 3

Describe and give examples of utility software

Answer 3

A piece of system software, with one specific purpose, that is used for the maintenance of the system

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

Question 4

Describe open-source software

Answer 4

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 5

Describe closed-source software (proprietary)

Answer 5

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 6

Describe and give examples of software libraries

Answer 6

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

• Examples: encryption and graphic routines

Question 7

What are the benefits of software libraries?

Answer 7

• 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 8

What are the negatives of using software libraries?

Answer 8

• 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 9

Describe machine code

Answer 9

• The output of a translator
• Uses binary notation (0101010101000011)
• Dependent on architecture
• Harder to program

Question 10

Describe high-level languages

Answer 10

• Not architecture specific
• Can be recompiled for different architectures.
• Close to English

Question 11

Describe assembly language

Answer 11

• Uses mnemonics to represent machine code instructions/opcodes
• Consists of simple instructions
• Specific to the instruction set of the given processor

Question 12

What is a translator?

Answer 12

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

Question 13

What are the 3 types of translators?

Answer 13

• Interpreter
• Compiler
• Assembler

Question 14

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

Answer 14

• 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 15

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

Answer 15

• 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 16

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

Answer 16

• 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 17

State the stages of compilation

Answer 17

• Lexical Analysis
• Syntax Analysis
• Code Generation
• Optimisation

Question 18

Describe the lexical analysis stage

Answer 18

• 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 19

Describe the syntax analysis stage

Answer 19

• 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 20

Describe the code generation stage

Answer 20

• 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 21

Describe code optimisation

Answer 21

• 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 22

Describe the purpose and types of linker

Answer 22

• 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

STATIC - Include full library in the final executable code
DYNAMIC - Points to the external libraries (adds a shortcut to it)

Question 23

Describe the purpose of a loader

Answer 23

• A program in an operating system (OS) used to load the executable file (exe) into memory from secondary storage.
• Loads the required software libraries