25. OCR A Level (H446) SLR5 – 1.2 Stages of compilation

What is the first stage of the compilation process?

• Lexical analysis

• Syntax analysis

• Code generation

• Code optimization

Answer explanation

The first stage of the compilation process is lexical analysis, which involves breaking the input into tokens. Syntax analysis, code generation, and code optimization come later in the process.

What does the lexical analyzer convert source code into?

• Machine code

• Symbol tables

• Abstract syntax trees

• A series of tokens

Answer explanation

The lexical analyzer converts source code into a series of tokens, which are the basic building blocks used for parsing and further processing the code.

What are considered valid tokens in programming languages?

• Syntax errors

• Comments and white spaces

• Keywords, constants, identifiers, strings, numbers, operators, and punctuation symbols

• Machine instructions

Answer explanation

Valid tokens in programming languages include keywords, constants, identifiers, strings, numbers, operators, and punctuation symbols.

What does the syntax analysis stage check?

• If the tokens are valid within the grammar of the language

• If the source code can be directly executed by the processor

• If the source code is optimized

• If the tokens can be converted into machine code

Answer explanation

The syntax analysis stage checks if the tokens are valid within the grammar of the language, ensuring correct syntax and structure.

What is the main output of the syntax analysis phase?

• An abstract syntax tree or parse tree

• A symbol table

• Machine code

• Optimized code

Answer explanation

The main output of the syntax analysis phase is an abstract syntax tree or parse tree, which represents the structure of the code without specific details like variable values or memory locations.

What is stored in a symbol table?

• The optimized version of the source code

• The syntax errors found in the source code

• The memory addresses of variables

• The tokens and their data types

Answer explanation

The symbol table stores the tokens and their data types, making it the correct choice.

What is the purpose of code optimization?

• To convert source code into machine code

• To reduce the overall execution time of the program

• To check the syntax of the source code

• To generate tokens from the source code

Answer explanation

Code optimization aims to reduce the overall execution time of the program by improving efficiency and performance.

What might code optimization remove from the final program?

• Valid tokens

• Syntax errors

• Redundant instructions and unreachable code

• Comments and white spaces

Answer explanation

Code optimization removes redundant instructions and unreachable code from the final program.

What is an example of a data type that cannot have its memory requirements known during compilation?

• Constants

• Dynamic data structures

• String

• Integer

Answer explanation

Dynamic data structures like linked lists or trees can grow or shrink during runtime, making it impossible to determine their memory requirements at compile time.

What does the compiler use to efficiently look up in the symbol table during the syntax analysis stage?

• An array

• A binary search tree

• A hash table

• A linear search algorithm

Answer explanation

During syntax analysis, the compiler uses a hash table to efficiently look up in the symbol table, providing quick access to symbols based on their hashed values.