Output of C programs | Set 61 (Loops)

Prerequisite : Loops in C
Q.1 What is the output of this program?

#include <iostream>
using namespace std;
int main()
{
    int i, j, var = 'A';

    for (i = 5; i >= 1; i--) {
        for (j = 0; j < i; j++)
            printf("%c ", (var + j));
        printf("\n");
    }
    return 0;
}

Options
a)A B C D E
A B C D E
A B C D E
A B C D E
A B C D E

b)A B C D
A B C D
A B C D
A B C D

c)A B C D
A B C
A B
A

d)A B C D E
A B C D
A B C
A B
A

ans:- d 

Explanation :- inner loop iterates for value less than equal to i, thus printing
A B C D E
A B C D
A B C
A B
A

Q.2 What is the output of this program?

#include <iostream>
using namespace std;
int main()
{
    int counter = 1;
    do {
        printf("%d, ", counter);
        counter += 1;
    } while (counter >= 10);
    printf("\nAfter loop counter=%d", counter);
    printf("\n");
    return 0;
}

Options

a) After loop counter=1
b) 1,
After loop counter=2
c) 1,
After loop counter=1
d) After loop counter=2

ans:- b

Explanation :- do while is an exit controlled loop, here loop body executed first, then condition will be checked.

Q.3 What is the output of this program?

#include <iostream>
using namespace std;
int main()
{
    int counter = 1;
    while (counter >= 10) {
        printf("%d, ", counter);
        counter += 1;
    }
    printf("\nAfter loop counter=%d", counter);
    printf("\n");
    return 0;
}

Options
a)After loop counter=1
b)1,
After loop counter=2
c)1,
After loop counter=1
d)After loop counter=2

ans:- a

Explanation :- since while is an entry controlled loop so, here condition will be checked first.

Q.4 What is the output of this program?

#include <iostream>
using namespace std;
int main()
{
    int loopvar = 10;
    while (printf("Hello ") && loopvar--)
        ;
    return 0;
}

Options
a)Hello
b)Hello Hello Hello Hello …….
c)Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello
d)Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello Hello

ans:- d

Explanation :- since post decrement operator is used so value is decremented after expression loopvar – – is evaluated. Thus, Hello is printed 11 times.

Q.5 What is the output of this program?

#include <iostream>
#include <string.h>
using namespace std;
int main()
{
    int counter = 1;
    while (counter <= 10 && 1 ++)
        printf("Hello");
    return 0;
}

Options

a)compilation error
b)HelloHello … 10 times
c)HelloHello … 11 times
d)Hello

ans:- a

Explanation :- Error: lvalue required as increment operand. It is a compile time error.