C Programming Interview / Viva Q&A: 1

Guess the output of this simple C program. You can check these 2 video tutorials listed below so that you get to know todays interview / viva question.

Related Read:
if else statement in C
Relational Operators In C

Whats the output of this C Program?

 
#include < stdio.h >

int main()
{
    int num;

    printf("Enter a number\n");
    scanf("%d", &num);

    if(num = 5)
    {
        printf("You entered number 5\n");
    }
    else
    {
        printf("You entered %d \n", num);
    }

    return 0;
}

If user enters num value as 10. What does the above C Program output?

Answer: Did you answer – You entered 10 as output? If yes, then its wrong.

Note:
1. If at first glance of the source code you didn’t get the answer right, then go through the videos I’ve posted in ‘Related Read” section above.
2. After going through the 2 videos I’ve posted in ‘Related Read’ section above, if you still didn’t get the answer, then please open your editor and type the program and execute it one line at a time.

Hint: assignment operator(=) and equality operator(==) are different and work differently in C programming.

C Programming Interview / Viva Q&A: 1

Here is the Answer:

As you can see in the condition of if, it’s written as num = 5. = is assignment operator. So here 5 is being assigned to variable num, and thus it returns 5. In C program, any non-zero number is considered as true. So every time the condition in if becomes true, so the block of code present in if gets executed. i.e., value of num is 5.

using equality operator for comparison

 
#include < stdio.h >

int main()
{
    int num;

    printf("Enter a number\n");
    scanf("%d", &num);

    if(num == 5)
    {
        printf("You entered number 5\n");
    }
    else
    {
        printf("You entered %d \n", num);
    }

    return 0;
}

Output 1:
Enter a number
10
You entered 10

Output 2:
Enter a number
5
You entered number 5

Output 3:
Enter a number
1000
You entered 1000

Note: Both programs are correct syntactically. That’s the reason compiler did not throw any error. It’s a logical error, so we need to be very careful while writing programs. If we do this simple logical error in a big program, it might take a lot of time to get to know the bug and fix it. So careful. Happy coding.

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