C Preprocessor Questions and Answers updated daily – C Language



11 C Preprocessor Questions and answers section with explanation for various online exam preparation, various interviews, C Language C Preprocessor online test. C Preprocessor Questions with detailed description, explanation will help you to master the topic.

C Preprocessor Questions

1.
     What will be the output of the program?

#include
#define MAX(a, b, c) (a>b ? a>c ? a : c: b>c ? b : c)

int main()
{
    int x;
    x = MAX(3+2, 2+7, 3+7);
    printf("%dn", x);
    return 0;
}



SHOW ANSWER
Correct Ans:10
Explanation:
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("%dn", x); It prints the value of 'x'.

Hence the output of the program is "10".


2.
    What will be the output of the program?

#include
#define PRINT(i) printf("%d,",i)

int main()
{
    int x=2, y=3, z=4;
    PRINT(x);
    PRINT(y);
    PRINT(z);
    return 0;
}



SHOW ANSWER
Correct Ans:2,3,4
Explanation:
The macro PRINT(i) print("%d,", i); prints the given variable value in an integer format.

Step 1: int x=2, y=3, z=4; The variable x, y, z are declared as an integer type and initialized to 2, 3, 4 respectively.

Step 2: PRINT(x); becomes printf("%d,",x). Hence it prints '2'.

Step 3: PRINT(y); becomes printf("%d,",y). Hence it prints '3'.

Step 4: PRINT(z); becomes printf("%d,",z). Hence it prints '4'.

Hence the output of the program is 2, 3, 4.


3.
 
What will be the output of the program?

#include<stdio.h>
#define MESS junk

int main()
{
    printf("MESSn");
    return 0;
}



SHOW ANSWER
Correct Ans:MESS
Explanation:
printf("MESSn"); It prints the text "MESS". There is no macro calling inside the printf statement occured.


4.
What will be the output of the program?

#include<stdio.h>
#define MIN(x, y) (x<y)? x : y;
int main()
{
    int x=3, y=4, z;
    z = MIN(x+y/2, y-1);
    if(z > 0)
        printf("%dn", z);
    return 0;
}



SHOW ANSWER
Correct Ans:3
Explanation:
The macro MIN(x, y) (x<y)? x : y; returns the smallest value from the given two numbers.

Step 1: int x=3, y=4, z; The variable x, y, z are declared as an integer type and the variable x, y are initialized to value 3, 4 respectively.

Step 2: z = MIN(x+y/2, y-1); becomes,

=> z = (x+y/2 < y-1)? x+y/2 : y - 1;

=> z = (3+4/2 < 4-1)? 3+4/2 : 4 - 1;

=> z = (3+2 < 4-1)? 3+2 : 4 - 1;

=> z = (5 < 3)? 5 : 3;

The macro return the number 3 and it is stored in the variable z.

Step 3: if(z > 0) becomes if(3 > 0) here the if condition is satisfied. It executes the if block statements.

Step 4: printf("%dn", z);. It prints the value of variable z.

Hence the output of the program is 3


5.
What will be the output of the program?

#include<stdio.h>
#define MAX(a, b) (a > b ? a : b)

int main()
{
    int x;
    x = MAX(3+2, 2+7);
    printf("%dn", x);
    return 0;
}



SHOW ANSWER
Correct Ans:9
Explanation:
The macro MAX(a, b) (a > b ? a : b) returns the biggest value of the given two numbers.

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

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

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

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

=> x = 9

Step 3 : printf("%dn", x); It prints the value of variable x.

Hence the output of the program is 9.


6.
What will be the output of the program?

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

int main()
{
    int va1=10;
    int va12=20;
    printf("%dn", FUN(va1, 2));
    return 0;
}



SHOW ANSWER
Correct Ans:20
Explanation:
The following program will make you understand about ## (macro concatenation) operator clearly.


7.
What will be the output of the program?

#include<stdio.h>
#define CUBE(x) (x*x*x)

int main()
{
    int a, b=3;
    a = CUBE(b++);
    printf("%d, %dn", a, b);
    return 0;
}



SHOW ANSWER
Correct Ans:27,6
Explanation:
The macro function CUBE(x) (x*x*x) calculates the cubic value of given number(Eg: 103.)

Step 1: int a, b=3; The variable a and b are declared as an integer type and varaible b id initialized to 3.

Step 2: a = CUBE(b++); becomes

=> a = b++ * b++ * b++;

=> a = 3 * 3 * 3; Here we are using post-increement operator, so the 3 is not incremented in this statement.

=> a = 27; Here, 27 is store in the variable a. By the way, the value of variable b is incremented by 3. (ie: b=6)

Step 3: printf("%d, %dn", a, b); It prints the value of variable a and b.

Hence the output of the program is 27, 6.


8.
What will be the output of the program?

#include<stdio.h>
#define SQR(x)(x*x)

int main()
{
    int a, b=3;
    a = SQR(b+2);
    printf("%dn", a);
    return 0;
}



SHOW ANSWER
Correct Ans:11
Explanation:
The macro function SQR(x)(x*x) calculate the square of the given number 'x'. (Eg: 102)

Step 1: int a, b=3; Here the variable a, b are declared as an integer type and the variable b is initialized to 3.

Step 2: a = SQR(b+2); becomes,

=> a = b+2 * b+2; Here SQR(x) is replaced by macro to x*x .

=> a = 3+2 * 3+2;

=> a = 3 + 6 + 2;

=> a = 11;

Step 3: printf("%dn", a); It prints the value of variable 'a'.

Hence the output of the program is 11


9.
What will be the output of the program?

#include<stdio.h>
#define MAN(x, y) ((x)>(y)) ? (x):(y);

int main()
{
    int i=10, j=5, k=0;
    k = MAN(++i, j++);
    printf("%d, %d, %dn", i, j, k);
    return 0;
}



SHOW ANSWER
Correct Ans:12,6,12
Explanation:
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, %dn", 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


10.
In which stage the following code 
#include<stdio.h> 
gets replaced by the contents of the file stdio.h



SHOW ANSWER
Correct Ans:During preprocessing
Explanation:
The preprocessor replaces the line #include <stdio.h> with the system header file of that name. More precisely, the entire text of the file 'stdio.h' replaces the #include directive.


11.
What will the SWAP macro in the following program be expanded to on preprocessing? will the code compile?

#include<stdio.h>
#define SWAP(a, b, c)(c t; t=a, a=b, b=t)
int main()
{
    int x=10, y=20;
    SWAP(x, y, int);
    printf("%d %dn", x, y);
    return 0;
}



SHOW ANSWER
Correct Ans:Not compile
Explanation:
The code won't compile since declaration of t cannot occur within parenthesis.



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