Relational operators in C - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of relational operators with integers

What is the output of the following C code?

C

#include <stdio.h>

int main() {
    int a = 5, b = 10;
    printf("%d\n", a < b);
    return 0;
}

A 10

B 0

C 5

D 1

💡 Hint

Remember that relational operators return 1 for true and 0 for false in C.

The expression 'a < b' is true because 5 is less than 10, so it returns 1.

❓ Predict Output

intermediate

Relational operator with equal values

What will be the output of this C program?

C

#include <stdio.h>

int main() {
    int x = 7, y = 7;
    printf("%d\n", x >= y);
    return 0;
}

A 1

B Error

C 0

D 7

💡 Hint

Check if x is greater than or equal to y.

Since x equals y, 'x >= y' is true and returns 1.

❓ Predict Output

advanced

Output of chained relational expressions

What is the output of this C code snippet?

C

#include <stdio.h>

int main() {
    int a = 3, b = 5, c = 7;
    printf("%d\n", a < b < c);
    return 0;
}

A Syntax Error

B 1

C 0

D 3

💡 Hint

Remember how relational operators associate and the result of comparisons in C.

The expression 'a < b < c' is evaluated left-to-right as '(a < b) < c'. 'a < b' is true (1), then '1 < c' (1 < 7) is true (1), so it prints 1.

❓ Predict Output

advanced

Relational operator with pointers

What will be the output of this C program?

C

#include <stdio.h>

int main() {
    int arr[3] = {1, 2, 3};
    int *p1 = &arr[0];
    int *p2 = &arr[2];
    printf("%d\n", p1 > p2);
    return 0;
}

A 0

B 1

C Undefined behavior

D Compilation error

💡 Hint

Compare the memory addresses pointed by p1 and p2.

Pointer p1 points to arr[0], which is at a lower address than p2 (arr[2]). So 'p1 > p2' is false (0).

🧠 Conceptual

expert

Behavior of relational operators with floating-point NaN

In C, what is the result of the expression (x < y) if x or y is NaN (Not a Number)?

A The expression causes a runtime error

B The expression evaluates to 1 (true)

C The expression evaluates to 0 (false)

D The expression causes a compilation error

💡 Hint

Think about how comparisons with NaN behave according to IEEE floating-point rules.

Any comparison involving NaN returns false except '!=' which returns true. So 'x < y' is false (0) if either is NaN.