Compilers

Question 1

4 stages of compilers / translation

Answer 1

• Lexical analysis
• Syntax analysis
• Code generation
• Code optimisation

Question 2

Lexical analysis

Answer 2

The process of breaking a string of program into a token list

• Spaces and comments are removed
• Goes through the code and tries to identify the following elements:

1. Identifiers (Variable names)
2. Keywords (Names built into the programming language e.g. if , while)
3. Separators(Punctuation)
4. Operators(+ , - , . =…….)
5. Literals(numbers)
6. Comments

These are formed in pairs knows as Tokens

Question 3

Lexemes

Answer 3

Invisible blocks of text that the compiler recognises

Question 4

Syntax analysis

Answer 4

Takes the tokenized code and applies the rules of the language to it
- Produces parse tree (also knows as an abstract syntax tree)
- Unnecessary details have been removed
- Here you will get error reports for incorrect code
-Tokens checked against rules

Question 5

Code generation

Answer 5

Abstract syntax tree is converted into object code (almost like machine code)
-addresses and scopes of variables are established

Question 6

Optimasation

Answer 6

Object code is converted into Optimised object code
- Requires to be parsed again (identify any inefficiencies)

Why this process is slow

Question 7

Libraries

Answer 7

Pre written code that can be called to add functionality to the programs

Question 8

Linkers

Answer 8

Copy compiled library code into the program
- adds to file size
- If library is referenced multiple times , the library code will be copied several times (leads to bloated programs)
- If libraries are updated the program will still keep the older version

Question 9

Loaders

Answer 9

Copies a reference of the compiled library code
- have not copied code so can not bloating code is not a problem
- several references will not increase file size
- updates to library can make code unstable

Question 10

Translators

Answer 10

Converts from source code (high / low level) to object code (machine / executable)

Question 11

Intermediate code

Answer 11

Code that is halfway between machine code and object code
- This is independent of the processor architecture so can be runacross different machines and operating systems.