Relational Operators in C

Relational operators compare two operands and determine the relationship between them.

int a = 10;
int b = 20;

printf("%d", a < b);

Since 10 is less than 20, the expression produces 1.

The == operator checks whether two values are equal.

int a = 10;
int b = 10;

printf("%d", a == b);

Output:

1

The result is 1 because both values are equal.

int a = 10;
int b = 20;

printf("%d", a == b);

Output:

0

The result is 0 because 10 and 20 are not equal.

The != operator checks whether two values are different.

int a = 10;
int b = 20;

printf("%d", a != b);

Output:

1

The result is 1 because the values are different.

int a = 10;
int b = 10;

printf("%d", a != b);

Output:

0

The result is 0 because the values are equal.

The > operator checks whether the left operand is greater than the right operand.

int a = 20;
int b = 10;

printf("%d", a > b);

Output:

1

int a = 10;
int b = 20;

printf("%d", a > b);

Output:

0

The expression is false because 10 is not greater than 20.

The < operator checks whether the left operand is less than the right operand.

int a = 10;
int b = 20;

printf("%d", a < b);

Output:

1

int a = 30;
int b = 20;

printf("%d", a < b);

Output:

0

The expression is false because 30 is not less than 20.

The >= operator checks whether the left operand is greater than or equal to the right operand.

int marks = 60;

printf("%d", marks >= 40);

Output:

1

The condition is true because 60 is greater than 40.

int marks = 40;

printf("%d", marks >= 40);

Output:

1

The condition is also true when both values are equal.

The <= operator checks whether the left operand is less than or equal to the right operand.

int age = 18;

printf("%d", age <= 18);

Output:

1

int age = 15;

printf("%d", age <= 18);

Output:

1

The condition is true because 15 is less than 18.

In C, a relational expression evaluates to an int value: 1 for true and 0 for false.

printf("%d\n", 10 > 5);
printf("%d\n", 10 < 5);

Output:

1
0

int age = 25;
int limit = 18;

int result = age > limit;

printf("%d", result);

Output:

1

The result can be stored in an integer variable.

Relational operators are frequently used with if statements.

int age = 20;

if (age >= 18)
{
    printf("Eligible");
}

The message is displayed because the condition is true.

int marks = 35;

if (marks >= 40)
{
    printf("Pass");
}
else
{
    printf("Fail");
}

Output:

Fail

#include <stdio.h>

int main()
{
    int age;

    printf("Enter your age: ");
    scanf("%d", &age);

    if (age >= 18)
    {
        printf("Adult");
    }

    return 0;
}

The relational operator compares the entered age with 18.

#include <stdio.h>

int main()
{
    int a, b;

    printf("Enter two numbers: ");
    scanf("%d %d", &a, &b);

    if (a > b)
    {
        printf("A is greater");
    }
    else if (a < b)
    {
        printf("B is greater");
    }
    else
    {
        printf("Both are equal");
    }

    return 0;
}

This program uses three relational comparisons to compare two numbers.

Characters can also be compared because character constants have integer values based on the execution character set.

char a = 'A';
char b = 'B';

printf("%d", a < b);

The result is commonly 1 in character sets where 'A' has a smaller value than 'B', such as ASCII.

float price = 99.5;

if (price > 50.0)
{
    printf("Price is greater than 50");
}

Relational operators can compare floating-point values as well.

A common beginner mistake is confusing assignment = with equality comparison ==.

int age = 20;

if (age == 20)
{
    printf("Age is 20");
}

Here, = assigns a value, while == compares values.

Relational expressions can be combined with logical operators to create more complex conditions.

int age = 25;
int marks = 70;

if (age >= 18 && marks >= 40)
{
    printf("Condition satisfied");
}

Here, two relational expressions are combined using logical AND.

#include <stdio.h>

int main()
{
    int a = 50;
    int b = 30;

    if (a > b)
    {
        printf("A is largest");
    }
    else
    {
        printf("B is largest");
    }

    return 0;
}

The > operator determines which number is larger.

#include <stdio.h>

int main()
{
    int marks = 55;

    if (marks >= 40)
    {
        printf("Pass");
    }
    else
    {
        printf("Fail");
    }

    return 0;
}

The >= operator checks whether the marks meet the minimum required value.

int number = 50;

if (number >= 1 && number <= 100)
{
    printf("Number is between 1 and 100");
}

The relational operators check both boundaries of the range.

• Using = instead of == for comparison.
• Confusing > with >=.
• Confusing < with <=.
• Forgetting that a false relational expression produces 0.
• Forgetting that a true relational expression produces 1.
• Using comparisons incorrectly inside complex conditions.

#include <stdio.h>

int main()
{
    int a, b;

    printf("Enter first number: ");
    scanf("%d", &a);

    printf("Enter second number: ");
    scanf("%d", &b);

    printf("Equal: %d\n", a == b);
    printf("Not Equal: %d\n", a != b);
    printf("Greater: %d\n", a > b);
    printf("Less: %d\n", a < b);
    printf("Greater or Equal: %d\n", a >= b);
    printf("Less or Equal: %d\n", a <= b);

    return 0;
}

This program demonstrates all six relational operators.

Practice the following programs:

1. Check whether two numbers are equal.
2. Check whether two numbers are different.
3. Find the greater number between two numbers.
4. Find the smaller number between two numbers.
5. Check whether a person is 18 or older.
6. Check whether marks are greater than or equal to 40.
7. Check whether a number is between 1 and 100.
8. Compare two decimal values.
9. Compare two character values.
10. Create a program that compares two numbers using all six relational operators.

Practice these comparisons with if and if-else statements to become comfortable with decision-making in C.