Preprocessor directive #ifdef .. #else ... #endif is used for conditional compilation.

True, the programmer tells the compiler to include the preprocessor when compiling.

False, the preprocessor cannot trap the errors, it only replaces the macro with the given expression. But the compiler will detect errors.

The macro MAX(a, b, c) (a>b ? a>c ? a : c: b>c ? b : c) returns the biggest of given three numbers.

Step 1: int x; The variable x is declared as an integer type.

Step 2: x = MAX(3+2, 2+7, 3+7); becomes,

=> x = (3+2 >2+7 ? 3+2 > 3+7 ? 3+2 : 3+7: 2+7 > 3+7 ? 2+7 : 3+7)

=> x = (5 >9 ? (5 > 10 ? 5 : 10): (9 > 10 ? 9 : 10) )

=> x = (5 >9 ? (10): (10) )

=> x = 10

Step 3: printf("%d\n", x); It prints the value of 'x'.

Hence the output of the program is "10".

The macro MAN(x, y) ((x)>(y)) ? (x):(y); returns the biggest number of given two numbers.

Step 1: int i=10, j=5, k=0; The variable i, j, k are declared as an integer type and initialized to value 10, 5, 0 respectively.

Step 2: k = MAN(++i, j++); becomes,

=> k = ((++i)>(j++)) ? (++i):(j++);

=> k = ((11)>(5)) ? (12):(6);

=> k = 12

Step 3: printf("%d, %d, %d\n", i, j, k); It prints the variable i, j, k.

In the above macro step 2 the variable i value is increemented by 2 and variable j value is increemented by 1.

Hence the output of the program is 12, 6, 12

The following program will make you understand about ## (macro concatenation) operator clearly.

#include<stdio.h>
#define FUN(i, j) i##j

int main()
{
    int First  	= 10;
    int Second  = 20;

    char FirstSecond[] = "CuriousTab";

    printf("%s\n", FUN(First, Second) );

    return 0;
}

Output:
-------
CuriousTab

The preprocessor will replace FUN(First, Second) as FirstSecond.

Therefore, the printf("%s\n", FUN(First, Second) ); statement will become as printf("%s\n", FirstSecond );

Hence it prints CuriousTab as output.

Like the same, the line printf("%d\n", FUN(va1, 2)); given in the above question will become as printf("%d\n", va12 );.

Therefore, it prints 20 as output.

False, A macro just replaces each occurrence with the code assigned to it. e.g. SQUARE(3) with ((3)*(3)) in the program.

A function is compiled once and can be called from anywhere that has visibility to the funciton.

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

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

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

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