Analyze the following C program (with real newlines) and select the best diagnosis:
#include
int main()
{
int i = 10, j = 20;
if(i = 5) && if(j = 10)
printf("Have a nice day");
return 0;
}
What is the correct compiler outcome?
-
AOutput: Have a nice day
-
BNo output (compiles and runs silently)
-
CError: Expression syntax
-
DError: Undeclared identifier “if”
-
EWarning only; then prints text
Answer
Correct Answer: Error: Expression syntax
Explanation
Introduction / Context:This question targets the grammar rules for if conditions and operator combining in C. It also probes whether assignment inside a condition is valid and how tokens like if may (or may not) appear within expressions.
Given Data / Assumptions:
- Two tokens “if” are written in an expression: if(i = 5) && if(j = 10).
- No extra parentheses group the statements as separate conditionals.
- Standard C syntax rules apply.
Concept / Approach:In C, the grammar requires an expression inside if ( ... ). The token if cannot appear as an operand within another expression. The sequence if(i = 5) && if(j = 10) attempts to chain two if statements using &&, which is syntactically invalid. While assignments inside a single if are allowed (e.g., if ((i = 5) && (j = 10))), embedding the keyword if in the middle of an expression is illegal.
Step-by-Step Solution:Parse: after the first ), the next token is &&, then “if” again.Since “if” cannot follow && as an expression operand, parsing fails.Compiler emits a syntax error; program does not compile.
Verification / Alternative check:Rewrite correctly: if ((i = 5) && (j = 10)) printf(...); compiles and prints.
Why Other Options Are Wrong:The program cannot produce output or run silently because it fails to compile. “Undeclared identifier if” is not the standard diagnostic; the core issue is syntax, not naming. “Warning only” understates the fatal error.
Common Pitfalls:Confusing the legal expression (i = 5) with the illegal keyword if embedded in expressions; forgetting parentheses when combining assignments with logical operators.
Final Answer:Error: Expression syntax