PAPER 1 • SOFTWARE AND SOFTWARE DEVELOPMENT • APPLICATIONS GENERATION

Compilation Stages

  • A compiler translates high-level source code into a form a computer can run. It does this in stages, beginning with lexical analysis and syntax analysis before moving on to code generation and optimisation.

Visual channel

Source code
Lexemes
Tokens
Abstract syntax tree
Object code
Dual coding

Verbal channel

  • Lexical analysis turns lexemes into tokens.
  • Syntax analysis checks grammar and builds a abstract syntax tree.
  • Code generation creates object code.
  • Optimisation improves speed and memory use.

Activity 1

Sort the compilation tasks

Drag each task into the correct stage. The statements come directly from the activity and answer decks.

Stage 1

Lexical analysis

Stage 2

Syntax analysis

Stage 3

Code generation

Stage 4

Optimisation

Activity 2

Lexical analysis practice

Source code

Function highest (num1 As Decimal, num2 As Decimal)
'Function to return the higher of two numbers
If num1 > num2 Then
  Return num1
Else
  Return num2
EndIf
EndFunction

Token format

[tokenclass:token]

Remember that comments and white space are ignored by the lexer.

Stage 1

Build the token stream

Continue the token stream for the source code using the format shown above.

Stage 2

Symbol table snapshot

Choose the token class and datatype for each of the tokens on this symbol table.1

1 Identifiers do not yet get their final datatype until the Syntax Analysis stage.

Activity 3

Syntax analysis studio

Stage 1

Checking the syntax

  • Trace the correct route through the syntax diagram for If num1 > num2 Then. Choose the pathway that matches the two operands. If you connect If through to Then correctly, you have followed a valid grammar rule.
If
Then

Stage 2

Build the abstract syntax tree

Drag the tokens into the correct places to build a hierarchical abstract syntax tree for If num1 > num2 Then.

Token class
Token
Token class
Token
Token class
Token
Token class
Token
Token class
Token

In syntax analysis, how is a abstract syntax tree created?

Stage 3

Update the symbol table

At syntax analysis, the compiler can now update the full symbol table and apply declared data types to the relevant identifiers.