Question 19

Statement I: 'Symbol table is accessed only during lexical analysis and syntax analysis.'

• The symbol table is a central data structure used throughout almost every compiler phase. Semantic analysis uses it to perform type checking and scope resolution; intermediate code generation uses it for address assignment; and code optimization/generation use it for register allocation and memory layouts.
• Hence, the symbol table is not accessed only during lexical and syntax analysis. Statement I is FALSE.

Statement II: 'Compilers for programming languages that support recursion necessarily need heap storage for memory allocation in the run-time environment.'

• Recursion requires a call stack (activation records pushed on call and popped on return) adhering to LIFO discipline.
• Heap storage is required only for dynamic memory allocation whose lifetime is independent of the call stack (e.g., manual allocation with malloc/new). Languages with recursion but without dynamic memory require only a stack, not a heap.
• Therefore, heap storage is not strictly necessary for recursion. Statement II is FALSE.

Statement III: 'Errors violating the condition any variable must be declared before its use are detected during syntax analysis.'

• Syntax analysis checks grammatical structure according to context-free grammar rules.
• Enforcing that an identifier is declared before its use is a context-sensitive requirement, checked during semantic analysis via symbol table lookups.
• Thus, this error is detected during semantic analysis, not syntax analysis. Statement III is FALSE.

Since all three statements are false, the correct answer is 'None of I, II, and III'.