Consider the following ANSI C program: int main() { Integer x; return 0; } Which one of the following phases in a seven-phase C compiler will throw an error?
Topic-wise GATE CS PYQs with verified steps
GATE CSE 2021 Set 2 · Q3
MCQ1 markEasy
Time
Consider the following ANSI C program:int main() {
Integer x;
return 0;
}Which one of the following phases in a seven-phase C compiler will throw an error?
Select one answerSingle correct
Pick an option to check
Solution
Step-by-step verified solution
Official answer: C) Semantic analyzer
Lexical Analysis, Parsing and SDTLexical Analyzer: Breaks the input source code into tokens.
Integerandxare both valid identifiers (tokens of type identifier), so no lexical error is generated.Syntax Analyzer (Parser): Validates the grammatical structure of the program based on Context-Free Grammar (CFG). The statement
Integer x;syntactically looks like<type_name> <identifier>;(or<identifier> <identifier>;), which fits the syntactic declaration rule.Semantic Analyzer: Responsible for type checking, undeclared variable/type detection, and scope resolution. Since
Integeris not defined as a valid data type (neither built-in nor declared viatypedef/struct), the semantic analyzer identifies thatIntegeris an undeclared type and reports a semantic error (e.g., *unknown type name 'Integer'*).Machine Dependent Optimizer: Executes much later in the backend; the compiler will fail before reaching this phase.
Therefore, the error is thrown during the Semantic analyzer phase (Option C).
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Examiner trap
The misconception this question tests
Consider which phase is responsible for type checking and verifying whether a data type identifier has been declared.
This Lexical Analysis, Parsing and SDT previous year question is Q3 of the GATE CSE 2021 Set 2 paper. Find more GATE CSE PYQs on Lexical Analysis, Parsing and SDT in Compiler Design, or browse all GATE CSE PYQs.
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Lexical Analysis, Parsing and SDT in GATE CSE
Lexical Analysis, Parsing and SDT has 14 GATE CSE PYQs across 12 papers from 2011 to 2025. 9 of them are 1-mark MCQs like this one, and it is the only one in GATE CSE 2021 Set 2.
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Independent practice explanation verified by the GateAI team. GATE is conducted by the IITs; question text follows the official paper.