APPLICATIONS GENERATION

Question 1

What is an application?

Answer 1

a program that can be run on a computer allowing the user to carry out specific tasks

Question 2

What is utility software?

Answer 2

system software with a specific purpose usually related to maintenance

Question 3

What are some examples of utility software?

Answer 3

• disk defragmentation - 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 these threats
• backup - automatically creates routine copies of specific files selected by the user. How often files are backed up is also specified by the user. This means that in the event of a power failure, malicious attack or other accident, files can be recovered

Question 4

What is open source software?

Answer 4

• software whose source code is freely available to view, redistribute or modify
• can be used without a license
• distributed with the source code

Question 5

What is closed source software?

Answer 5

• requires the user to hold an appropriate
  license to use the source code.
• users cannot access the source code as the company owns the copyright license

Question 6

What are the advantages of open source software?

Answer 6

• can be modified - improvements made and also can be made more specific for certain problems
• usually free
• new features regularly added as the code is continually being developed in a collaborative way

Question 7

What are the disadvantages of open source software?

Answer 7

• lack of support
• lower security as it may not be developed in a controlled environment

Question 8

What are the advantages of closed source software?

Answer 8

• regular well tested updates
• high level of security
• support provided by company that owns the software

Question 9

What are the disadvantages of closed source software?

Answer 9

• restrictions on use
• cost
• software can’t be modified by users

Question 10

What is a translator?

Answer 10

a program which converts code from one computer language to another

Question 11

What are the 3 types of translator?

Answer 11

• assembler
• compiler
• interpreter

Question 12

Compiler

Answer 12

• translate high-level code into machine code all at once
• initial compilation process is longer than using other translators
• compiled code is platform-specific
• doesn’t require original source code to be executed

Question 13

Interpreter

Answer 13

• translate and execute code line-by-line
• calls subroutines within its own code to execute a program
• produce an error if a line contains an error
• slower than running compiled code
• correct interpreter required to run on different platforms
• code is platform-independent
• useful for testing code

Question 14

Assembler

Answer 14

• assembly code is a low-level language that is platform specific
• assemblers translate assembly code into machine code
• each line of assembly code is equivalent to almost one line of machine code.

Question 15

What are the 4 stages of compilation?

Answer 15

• 1 - lexical analysis
• 2 - syntax analysis
• 3 - code generation
• 4 - code optimisation

Question 16

Lexical analysis

Answer 16

• whitespace and comments are remove
• keywords and identifiers are replaced with tokens
• information about tokens is stored in a symbol table

Question 17

Syntax analysis

Answer 17

• tokens analysed against rules of the programming language
• syntax errors are flagged up
• abstract syntax tree is produced

Question 18

Code generation

Answer 18

• abstract syntax tree used to produce machine code

Question 19

Code optimisation

Answer 19

• object code is made as efficient as possible by
  removing redundancies to produce code that gives the same result
• aims to reduce execution time
• very time-consuming stage

Question 20

What is a linker?

Answer 20

a program which places the appropriate machine addresses in the call and returns instructions of a compiled program so all the other required object code files and modules are linked together

Question 21

What is a loader?

Answer 21

a program that loads the executable object program and its associated libraries into memory before it is run

Question 22

What are libraries?

Answer 22

a collection of programs which are already compiled and can be loaded into a program and run whenever required

Question 23

What are the advantages of using a library?

Answer 23

• error-free
• save time and effort of developing and testing modules
• can be reused across multiple programs