C Preprocessor

Preprocessor directive #undef can be used only on a macro that has been #define earlier

A:

True

B:

False

C:

D:

Answer: A

True, #undef can be used only on a macro that has been #define earlier

Example: #define PI 3.14

We can undefine PI macro by #undef PI

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If the file to be included doesn't exist, the preprocessor flashes an error message.

A:

True

B:

False

C:

D:

Answer: A

True, the included file does not exist it will generate the error.

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Which of the following are correctly formed #define statements in C?

A:

#define CUBE (X) (X*X*X);

B:

#define CUBE(x) (X*X*X)

C:

#define CUBE(X)(X*X*X)

D:

#define CUBE(X) {X*X*X}

Answer: C

No answer description is available. Let's discuss.

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Which of the following are correct preprocessor directives in C?

1:	#ifdef
2:	#if
3:	#elif
4:	#undef

A:

1, 2

B:

4

C:

1, 2, 4

D:

1, 2, 3, 4

Answer: D

The macros #ifdef #if #elif are called conditional macros.

The macro #undef undefine the previosly declared macro symbol.

Hence all the given statements are macro preprocessor directives.

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Point out the error in the program

#include<stdio.h>

int main()
{
    int i;
    #if A
        printf("Enter any number:");
        scanf("%d", &i);
    #elif B
        printf("The number is odd");
    return 0;
}

A:

Error: unexpected end of file because there is no matching #endif

B:

The number is odd

C:

Garbage values

D:

None of above

Answer: A

The conditional macro #if must have an #endif. In this program there is no #endif statement written.

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Questions for: C Preprocessor