Question 1

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

Accepted Answer

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

Question 2

Once preprocessing is over and the program is sent for the compilation the macros are removed from the expanded source code.

Accepted Answer

True, After preprocessing all the macro in the program are removed.

Question 3

Every C program will contain at least one preprocessor directive.

Accepted Answer

False, the preprocessor directive is not mandatory in any c program.

Question 4

A header file contains macros, structure declaration and function prototypes.

Accepted Answer

True, the header file contains classes, function prototypes, structure declaration, macros.

Question 5

In a macro call the control is passed to the macro.

Accepted Answer

False, Always the macro is substituted by the given text/expression.

Question 6

A preprocessor directive is a message from compiler to a linker.

Accepted Answer

FALSE Example: #define symbol replacement When the preprocessor encounters #define directive, it replaces any occurrence of symbol in the rest of the code by replacement. This replacement can be an statement or expression or a block or simple text.

Question 7

A macro must always be defined in capital letters.

Accepted Answer

FALSE, The macro is case insensitive.

Question 8

Macros with arguments are allowed

Accepted Answer

True, A macro may have arguments. Example: #define CUBE(X)(X*X*X)

Question 9

Macros have a local scope.

Accepted Answer

False, The scope of macros is globals and functions. Also the scope of macros is only from the point of definition to the end of the file.

Question 10

There exists a way to prevent the same file from getting #included twice in the same program.

Accepted Answer

True, We can prevent the same file from getting included again by using a preprocessor directive called #ifndef (short for "if not defined") to determine whether we've already defined a preprocessor symbol called XSTRING_H. If we have already defined this symbol, the compiler will ignore the rest of the file until it sees a #endif (which in this case is at the end of the file). #ifndef XSTRING_H #define XSTRING_H defines the same preprocessor symbol, Finally, the last line of the file, #endif

Question 11

Will the following program print the message infinite number of times? #include<stdio.h>
#define INFINITELOOP while(1)

int main()
{
    INFINITELOOP
    printf("CuriousTab");
    return 0;
}

Accepted Answer

Yes, the program prints "CuriousTab" and runs infinitely. The macro INFINITELOOP while(1) replaces the text 'INFINITELOOP' by 'while(1)' In the main function, while(1) satisfies the while condition and it prints "CuriousTab". Then it comes to while(1) and the loop runs infinitely.

Question 12

Will the program compile successfully? #include<stdio.h>

int main()
{
    #ifdef NOTE
        int a;
        a=10;
    #else
        int a;
        a=20;
    #endif
    printf("%d
", a);
    return 0;
}

Accepted Answer

Yes, this program will compile and run successfully and prints 20. The macro #ifdef NOTE evaluates the given expression to 1. If satisfied it executes the #ifdef block statements. Here #ifdef condition fails because the Macro NOTE is nowhere declared. Hence the #else block gets executed, the variable a is declared and assigned a value of 20. printf("%d
", a); It prints the value of variable a 20.

Question 13

Would the following typedef work? typedef #include l;

Accepted Answer

Because typedef goes to work after preprocessing.

Question 14

Will the program compile successfully? #include<stdio.h>
#define X (4+Y)
#define Y (X+3)

int main()
{
    printf("%d
", 4*X+2);
    return 0;
}

Accepted Answer

Reports an error: Undefined symbol 'X'

Question 15

It is necessary that a header files should have a .h extension?

Accepted Answer

No, the header files have any kind of extension.

Question 16

Will the program compile successfully? #include<stdio.h>

int main()
{
    printf("India" "CURIOUSTAB
");
    return 0;
}

Accepted Answer

Yes, It prints "CuriousTab"

Question 17

Will it result in to an error if a header file is included twice?

Accepted Answer

Unless the header file has taken care to ensure that if already included it doesn't get included again. Turbo C, GCC compilers would take care of these problems, generate no error.

C Preprocessor Questions