GATE CS 2026 Set 1 Q.27: Lexical Analysis

Consider the following C statements:

char *str1 = "Hello;                  /* Statement S1 */
char *str2 = "Hello;";                /* Statement S2 */
int *str3 = "Hello";                  /* Statement S3 */

Which of the following options is/are correct?

S1 and S2 have syntactic errors

S2 has a lexical error and S3 has a syntactic error

S1 has a lexical error and S3 has a semantic error

S1 has a syntactic error and S3 has a semantic error

Official answer and solution

Official answer: C
From: Official GATE 2026 answer key

Solution

Classify the error in each statement according to the compiler phase (lexical, syntax, or semantic analysis) that detects it.

Statement S1 (char *str1 = "Hello;): The opening double quote is never closed before the end of the line, so the scanner cannot form a valid string literal token. This is a lexical error.
Statement S2 (char *str2 = "Hello;";): The semicolon inside quotes is part of the string literal, and the statement ends with a valid semicolon. S2 has no error.
Statement S3 (int *str3 = "Hello";): S3 is lexically and syntactically well-formed, but initializes an int * pointer with a string literal of type char * (char[6]), violating C type compatibility rules during semantic analysis.

Final answer

Option (C)

Common trap

Classifying an unterminated string literal in S1 as a syntactic error instead of a lexical error.

The answer is the one in the official GATE answer key. The solution is this site's own explanation.

Source

Paper: GATE 2026 Computer Science and Information Technology - Session 1 (CS1)
Question: 27 of 65
Section: Computer Science and Information Technology

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