Output of C programs | Set 42

QUE.1 What is the output of following program? 

#include <stdio.h>
int main()
{
    int x = 10, *y, **z;

    y = &x;
    z = &y;
    printf("%d %d %d", *y, **z, *(*z));
    return 0;
}

a. 10 10 10 
b. 100xaa54f10 
c. Run time error 
d. No Output 

Answer : a

Explanation: Because y contains the address of x so *y print 10 then **z contains address of y of x so print the value of x 10 and 3rd *(*z) contains address of y of x that's why print 10. So, final output is 10 10 10.

QUE.2 What is the output of following program? 

#include <stdio.h>
int main()
{
    // initialize the val=1
    int val = 1;

    do {
        val++;
        ++val;
    } while (val++ > 25);
    printf("%d\n", val);
    return 0;
}

a) 25 
b) 50 
c) 12 
d) 4 

Answer : d

Explanation: Here, do while loop executes once and then it will check condition while will be false meanwhile value will be increased 3 times (two times in do while body and once while checking the condition); 
Hence value will be 4.

QUE.3 What is the output of following program in the text file?  

#include <stdio.h>
int main()
{
    int a = 1, b = 2, c = 3;
    char d = 0;
    if (a, b, c, d) {
        printf("enter in the if\n");
    }
    printf("not entered\n");
    return 0;
}

a) enter in the if 
b) not entered 
c) run time error 
d) segmentation fault 

Answer : b

Explanation: In this program, We are check the if condition all (a, b, c)>0 but d = 0 so condition is false didn't enter in the if so print not entered.

QUE.4 What is the output of following program?  

#include <stdio.h>
int main()
{
    char str[10] = "Hello";
    printf("%d, %d\n", strlen(str), sizeof(str));
    return 0;
}

a) 5, 10 
b) 10, 5 
c) 10, 20 
d) None of the mentioned 

Answer: a

Explanation: strlen gives length of the string that is 5; sizeof gives total number of occupied memory for a variable that is 8; since str is a pointer so sizeof(str) may be 2, 4 or 8. 
It depends on the computer architecture.

QUE.5 What is the output of following program?  

#include <stdio.h>
int main()
{
    if (0)
        ;
    printf("Hello");
    printf("Hi");
    return 0;
}

OPTION 
a) Hi 
b) HelloHi 
c) run time error 
d) None of the mentioned 

Answer : b

Explanation: There is a semicolon after the if statement, so this statement will be considered as a separate statement; and here printf("Hello"); will not be associated with the if statement. Both printf statements will be executed.