C | Macro & Preprocessor | Question 2

C

#include <stdio.h>
#if X == 3
    #define Y 3
#else
    #define Y 5
#endif

int main()
{
    printf(\"%d\", Y);
    return 0;
}

What is the output of the above program?

(A)

3

(B)

5

(C)

3 or 5 depending on value of X

(D)

Compile time error

Answer: (B)

Explanation:

In the first look, the output seems to be compile-time error because macro X has not been defined. In C, if a macro is not defined, the pre-processor assigns 0 to it by default. Hence, the control goes to the conditional else part and 5 is printed. See the next question for better understanding.

Quiz of this Question
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