Applications generation - paper 1

Question 1

What are the two types of software?

Answer 1

Applications software
Systems software

Question 2

What is open source code?

Answer 2

Open source code can be used by anyone without a license and is distributed with the source code.

Question 3

What is closed source code?

Answer 3

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

Question 4

Advantages of open source code?

Answer 4

Can be modified and improved by anyone
Technical support from online community
Can be modified and sold on

Question 5

Advantages of closed source code?

Answer 5

Thorough, regular and well tested updates
Company owning software provides expert support and user manuals
High levels of security as developed professionally.

Question 6

Disadvantages of open source code?

Answer 6

Support available online may be insufficient or incorrect. No user manuals
Lower security as may not be developed in a controlled enviroment

Question 7

Disadvantages of closed source code?

Answer 7

License restricts how many people can use the software at once
Users cannot modify and improve software themselves.

Question 8

What are different types of translators?

Answer 8

Compiler, interpreter, assembler

Question 9

What is a compiler?

Answer 9

Compilers translate high level code into machine code all at once. The initial compilation process is longer than using an interpreter or an assembler, if changes are made the whole code must be re compiled.

Question 10

What is an interpreter?

Answer 10

An interpreter translates and executes code line by line.
Initially appear faster however slowed than running compiled code
Useful for testing sections of code and pinpointing errors

Question 11

What is an assembler?

Answer 11

An assembler translates assembly code into machine code
Assembly code is platform specific as instructions are processor specific

Question 12

What are the four different stages of compilation?

Answer 12

Lexical
Syntax
Code generation
Optimisation

Question 13

What happens in lexical analysis?

Answer 13

White spaces and comments are removed from the code
Keywords and names of variables are replaced with tokens that are stored in a symbol table

Question 14

What happens in syntax analysis?

Answer 14

Tokes are analysed against rules are programming language
Any tokes that break the rules are flagged for a syntax error
Syntax tree is produced that represents the code as a tree

Question 15

What happens in the code generation stage of compilation?

Answer 15

The syntax tree produced is used to produce machine code.

Question 16

What happens in optimisation stage of compilation?

Answer 16

Goes through the code and looks for ways to make it more efficient
Aims to make the code faster to execute- however does take time looking for ways to make the code more efficient
Redundant parts of code are removed.

Question 17

What is a linker?

Answer 17

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

Question 18

What is a static linker?

Answer 18

Modules and libraries are added directly into the file.
Increases the size of the file

Question 19

What is a dynamic linker?

Answer 19

Addresses of modules and libraries are included in the file where they are referenced.
Keeps files small and external updates are gulag to the file

Question 20

What is a loader?

Answer 20

Loaders are programs that are provided by the operating system
When a file is executed the loader retrieves the library or subroutine from the given memory location