Application Generation

Question 1

What is Application Software

Answer 1

Software designed to be used by the end-user to perform one specific task. It requires systems software in order to run

Question 2

What is System Software

Answer 2

• Software that is responsible for running the computer system smoothly in the background
• It interacting with hardware and providing a platform for applications software to run
• The user does not directly interact with systems software but it ensures high performance for the user

Question 3

Describe examples of application software and system software

Answer 3

• Application software - desktop publishing, word processing, spreadsheets, web browsers
• System software - library programs, utility programs, operating system, device drivers

Question 4

What are Utilities

Answer 4

Operations that run in the background and maintain a high-performing operating system. Each has a specific function and each runs without user interaction

Question 5

Describe Examples of System Utilities

Answer 5

• Compression - enable files to be compressed and decompressed. This is used when compressing large files to be transmitted across the Internet and to compress scanned files
• Disk defragmentation - as the hard disk becomes full files become fragmented (when files are stored in different parts of memory). The disk defragmenter utility rearranges the contents of the hard drive so they can be accessed faster, thus improving performance
• Antivirus - responsible for detecting potential threats to the computer, alerting the user and removing the threats
• Automatic updating - ensures the operating system is kept up to date, with any updates being automatically installed when the computer is restarts
• Backup - this automatically creates routine copies of specific files selected by the user. This means that in the event of a power failure, attack or accident, files can be recovered
• Task Manager - this allows the user to manage, maintain and control computer resources in order to maximum their CPU time for a specific task
• Software Firewall - acts as a filter for data entering or leaving a network or computer to stop harmful actions getting access

Question 6

What is Open Source Code

Answer 6

Code that is freely available to edit, ammend or recomplie

Question 7

What is Closed Source Code

Answer 7

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

Question 8

What are the Advantages and Disadvantages of Open and Closed Source Code

Answer 8

Open Source

• Advantages - improved by community effort, technical support from online community, can be modified and sold on
• Disadvantages - support available online may be insufficient or incorrect, lower security

Closed Source

• Advantages - regular and well-tested updates, expert support and user manuals, high levels of security as developed professionally
• Disadvantages - license has restrictions about use, users cannot modify and improve code

Question 9

Explain why all closed source software is most likely to be compiled rather than run on an interpreter

Answer 9

• Closed Source translate the source code prior to distribution
• Meaning the user gets an executable program
• Do not need to check for errors as code is already executable

Question 10

What are the factors to consider when choosing between open and close source code

Answer 10

• Costs - implementation, maintenance, training of staff, license
• Functionality - features available, ease of use

Question 11

What is a translator

Answer 11

A program that converts high-level source code into low-level object code

Question 12

What are the Three Types of Translators

Answer 12

• Assembler
• Compiler
• Interpreter

Question 13

What is Machine Code

Answer 13

A programming language that consists of instructions written in binary

Question 14

What is Higher Level Language

Answer 14

A programming language closer to a the programmer’s spoken/written language

Question 15

What is Low Level Language

Answer 15

A programming language closer to a computer’s instruction set

Question 16

What is Assembly Language

Answer 16

• A low level language that uses mneomincs to represent instructions
• The instruction is divided up into operand and opcode

Question 17

What does an Assembler do

Answer 17

Translates assembly code into machine code

Question 18

What does a Compiler do

Answer 18

Translates high-level code into machine code all at once

Question 19

What does an Interpreter do

Answer 19

Translates high-level code into machine code and execute code line-by-line

Question 20

What are the Advantages and Disadvantages of Assemblers, Compilers and Interpreters

Answer 20

Question 21

What are the stages of Compilation

Answer 21

• Lexical Analysis
• Syntax Analysis
• Code Generation
• Optimisation

Question 22

What happens during Lexical Analysis

Answer 22

• Whitespace and comments are removed
• Keywords and identifiers are replaced with tokens
• Tokens are stored in the symbol table

Question 23

What happens during Syntax Analysis

Answer 23

• Tokens analysed against rules of the programming language
• Syntax errors are identified and added to a list of errors
• Details e.g. data types, added to symbol table
• Abstract syntax tree is produced (a representation of the source code in the form of a tree)

Question 24

What happens during Code Generation

Answer 24

Abstract syntax tree used to produce machine code

Question 25

What happens during Optimisation

Answer 25

* Searches through the code for areas it could be made more efficient and faster to execute * This is a very time-consuming stage * Redundant parts of code are removed

Question 26

What types of things are removed during the Optimisation Stage of Compiling

Answer 26

* Redundnat instructions * Subroutines that are never called * Variables that are never referenced

Question 27

What is a Linker

Answer 27

A piece of software that is responsible for linking external modules and libraries included within the code

Question 28

If a game uses a 2D graphics library, explain why a linker would need to be used after compilation

Answer 28

* The user running the program will not necessarily have the library installed on their machine * Therefore the relevant code needs to be included within the final executable * It is the job of the linker to combine this code

Question 29

What are the two different types of Linkers

Answer 29

* Static Linker - module/library code is copied directly into the file. Increases the size of the file. * Dynamic Linker- Addresses of modules/ libraries are added to the file. External module/library updates automatically feed through to the main file

Question 30

What is the advantage of a Dynamic Linker over a Static Linker

Answer 30

* Files remain small * External updates feed through to the main file so there is no need to rewrite the code

Question 31

What are Loaders

Answer 31

Programs provided by the operating system that fetch the library/ module from the given memory location

Question 32

What are Libraries

Answer 32

Pre-compiled programs which can be incorporated within other programs using either static or dynamic linking

Question 33

What are the advantages of using Libraries

Answer 33

* Error-free * Save time and effort of developing and testing modules * Can be reused across multiple programs * Save programmers from ‘reinventing the wheel’

Question 34

What are the disadvantages of using Libraries

Answer 34

* Must be well written - the library has to be well-written and robust or it will impair all applications making use of it * Can be expensive - specialist libraries for engineering, science and finance can be very expensive * For run-time loading the library has to be present on the computer running the application

Question 35

What are the Advanatges and Disadvantages of Static and Dynmaic Linkers

Answer 35

* Static - * Execution faster because you don't need to cross local files * Compilation takes longer since you are adding to the size of the file Dynamic - * Smaller files in main code * Libraries must be preset on any machine using it