Relational Operators

Relational Operators × if–else

An interactive blog post — type values for a and b, and see which comparisons are true vs false.

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Essay: Relational Operators & If–Else

In programming, decision-making is essential. A program often needs to choose one path over another— for example, to approve a login, assign a grade, or show a warning. These choices are driven by relational operators working together with the if–else statement.

What are Relational Operators?

Relational operators compare two values and yield a Boolean result: true or false. They do not change the values; they simply test the relationship between them. The most common ones are:

• == (equal to) — checks whether two values are the same.
• != (not equal to) — checks whether two values differ.
• > (greater than) — true when the left value is larger than the right.
• < (less than) — true when the left value is smaller than the right.
• >= (greater than or equal to) — true when the left is larger than or equal to the right.
• <= (less than or equal to) — true when the left is smaller than or equal to the right.

Because a comparison returns only true or false, these operators fit naturally inside conditions.

How If–Else Uses Them

The if statement evaluates a condition. If it is true, the if block runs; otherwise, the else block runs. Here is a classic example that checks eligibility based on age:

int age = 16;

if (age >= 18) {
    printf("You can vote");
} else {
    printf("You are too young to vote");
}

In this program, the relational operator >= compares age with 18. If the result is true, the first message is printed; otherwise, the second.

Why They Matter

Together, relational operators and if–else enable programs to react to data: validate inputs, branch logic, and implement algorithms such as searching and sorting. Without them, code would execute in a straight line with no ability to choose different actions based on conditions.

Scroll down to the interactive section to try the operators live with your own values for a and b.

1) Enter values

a

b

---

Tip: You can use arrow keys while focused in a number field to change values. The comparisons update instantly.

2) What are relational operators?

They compare two values and return a Boolean — either true or false. We’ll evaluate all six common operators below.

• == equal to
• != not equal to
• > greater than
• < less than
• >= greater than or equal to
• <= less than or equal to

3) Live evaluation

==

a == b

—

!=

a != b

—

>

a > b

—

<

a < b

—

>=

a >= b

—

<=

a <= b

—

4) if–else in action

Pick a condition a == b a != b a > b a < b a >= b a <= b

Choose a condition to see which branch runs.

Under the hood, each condition evaluates to true/false. The if block runs when it’s true; otherwise the else block runs.

5) Assignments (with answers)

Practice these and expand them as mini-programs. Click to show/hide the answers.

1. Compare two numbers: Read a and b. Print which one is larger or if they are equal.

   Answer

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

2. Equality check: Print "Equal" if a == b otherwise "Not equal".

   Answer

   if (a == b) printf("Equal"); else printf("Not equal");

3. Number in range: Print "In Range" if a is between 10 and 20 (inclusive).

   Answer

   if (a >= 10 && a <= 20) printf("In Range"); else printf("Out of Range");

4. Absolute difference: Print the absolute difference between a and b using only relational operators and subtraction.

   Answer

   int diff;
   if (a >= b) diff = a - b; else diff = b - a;
   printf("%d", diff);

5. Min and Max: Set max to the larger of a, b; set min to the smaller.

   Answer

   int max, min;
   if (a >= b) { max = a; min = b; }
   else        { max = b; min = a; }

6. Sign comparison: Print "Same sign" if a and b are both non-negative or both negative; else "Different".

   Answer

   if ((a >= 0 && b >= 0) || (a < 0 && b < 0)) printf("Same sign");
   else printf("Different");

7. Close enough (tolerance): For floating values, print "Close" if |a - b| <= 0.001.

   Answer

   double diff = (a >= b) ? (a - b) : (b - a);
   if (diff <= 0.001) printf("Close"); else printf("Far");

8. Odd/even relation: If both numbers are even or both odd, print "Same parity"; otherwise "Different parity".

   Answer

   int aEven = (a % 2 == 0);
   int bEven = (b % 2 == 0);
   if ((aEven && bEven) || (!aEven && !bEven)) printf("Same parity");
   else printf("Different parity");

9. Grade boundary: Given a mark a, print "Pass" if a >= 33 else "Fail".

   Answer

   if (a >= 33) printf("Pass"); else printf("Fail");

10. Between two numbers: Given x, check if it lies between a and b regardless of which is larger.

    Answer

    int low, high;
    if (a <= b) { low = a; high = b; } else { low = b; high = a; }
    if (x >= low && x <= high) printf("Yes"); else printf("No");

6) Contact & Progress

If you have questions or want to share your solutions, reach out directly:

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Assignments Checklist

• Assignment 1
• Assignment 2
• Assignment 3
• Assignment 4
• Assignment 5
• Assignment 6
• Assignment 7
• Assignment 8
• Assignment 9
• Assignment 10

6) Track your progress

Select the assignments you’ve completed. Your progress is saved in your browser.

1) Compare two numbers 2) Equality check 3) Number in range 4) Absolute difference 5) Min and Max 6) Sign comparison 7) Close enough (tolerance) 8) Odd/even relation 9) Grade boundary 10) Between two numbers

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