What Is an Operator in C?

In simple terms, an operator is a symbol that tells the compiler to perform a specific operation on one or more values (operands).

Example:

int a = 10, b = 3;
int c = a + b;

• + is the operator.
• a and b are the operands.
• a + b is an expression.

Main Categories of C Operators (Beginner Level)

C has many operators, but for beginner/technician level we mainly focus on four important groups:

• Arithmetic operators – for basic math.
• Relational operators – for comparisons (greater than, equal, etc.).
• Logical operators – for combining conditions (AND, OR, NOT).
• Assignment operators – for storing results in variables.

We will go through each group slowly with examples.

Arithmetic Operators in C

Arithmetic operators do basic mathematical operations – just like calculator buttons. They work with numeric data types such as int, float and double.

Simple Example

#include <stdio.h>

int main() {
    int a = 10, b = 3;
    printf("a + b = %d\\n", a + b);
    printf("a - b = %d\\n", a - b);
    printf("a * b = %d\\n", a * b);
    printf("a / b = %d\\n", a / b);  // integer division
    printf("a %% b = %d\\n", a % b); // note: %% prints %
    return 0;
}

Arithmetic with float/double

float x = 10.0f, y = 3.0f;
printf("x / y = %.2f\\n", x / y);   // 3.33

When both operands are floating type, the result is also floating with decimal part.

Unary +, -, ++ and — Operators

Some arithmetic operators work with only one operand. These are called unary operators.

• + – unary plus (usually not needed).
• - – unary minus, changes sign.
• ++ – increment by 1.
• -- – decrement by 1.

Unary Minus

int a = 5;
int b = -a;   // b becomes -5

Increment and Decrement

++ and -- are used very often in loops and counters.

int count = 0;
count++;    // count becomes 1
count++;    // count becomes 2
count--;    // count becomes 1 again

Prefix vs Postfix (++i and i++)

Increment/decrement has two forms:

• Prefix: ++i – first increment, then use the value.
• Postfix: i++ – first use the value, then increment.

int i = 5;
printf("%d\\n", ++i);   // prints 6 (i becomes 6 before printing)
printf("%d\\n", i++);   // prints 6 (then i becomes 7)
printf("%d\\n", i);     // prints 7

Relational Operators – Comparing Values

Relational operators are used to compare two values. Result is either true (1) or false (0). They are mainly used inside if, while, for conditions.

Using Relational Operators in if…else

#include <stdio.h>

int main() {
    int marks;
    printf("Enter your marks: ");
    scanf("%d", &marks);

    if (marks >= 50) {
        printf("Result: PASS\\n");
    } else {
        printf("Result: FAIL\\n");
    }

    return 0;
}

Logical Operators – Combining Conditions

When you need to check more than one condition at the same time, you use logical operators. These work on conditions that are already true (1) or false (0).

AND (&&) Truth Table

OR (||) Truth Table

Example – Checking Range with &&

// Check if temperature is in normal range
if (temp >= 20 && temp <= 30) {
    printf("Temperature OK\\n");
} else {
    printf("Temperature OUT OF RANGE\\n");
}

Example – Checking Multiple Options with ||

// Check if user typed Y or y
if (ch == 'Y' || ch == 'y') {
    printf("You selected YES\\n");
}

Assignment & Compound Assignment Operators

Assignment operators are used to store a value into a variable. The simplest one is =.

Simple Assignment

int a;
a = 10;        // assign 10 to a

float x = 5.5; // declaration + assignment

Many times we do an operation and immediately assign back to the same variable. Instead of writing long expressions, C provides compound assignment operators.

Example – Using Compound Assignment

int total = 0;
total += 5;   // total = 5
total += 10;  // total = 15
total -= 3;   // total = 12
printf("Total = %d\\n", total);

These operators make your code shorter and clearer, especially when working with counters, sums and averages.

Combined Example – Checking Bill Discount

Let us combine arithmetic, relational, logical and assignment operators in a small program.

#include <stdio.h>

int main() {
    float amount;
    float discount = 0.0f;

    printf("Enter total bill amount: ");
    scanf("%f", &amount);

    // Apply discount: 5% for 1000–4999, 10% for 5000 and above
    if (amount >= 1000 && amount < 5000) {
        discount = amount * 0.05f;   // arithmetic + assignment
    } else if (amount >= 5000) {
        discount = amount * 0.10f;
    }

    amount -= discount;     // compound assignment

    printf("Discount given = %.2f\\n", discount);
    printf("Final amount to pay = %.2f\\n", amount);

    return 0;
}

In this program we used:

• Arithmetic: * and -
• Relational: >=, <
• Logical: &&
• Assignment: =, -=

Operator Precedence (Which Is Done First?)

When an expression uses more than one operator, C follows precedence rules to decide which operation to perform first.

Simple Rule (Beginner Level)

• Parentheses () first.
• Then unary operators: ++ -- + - !
• Then multiplication/division/modulus: * / %
• Then addition/subtraction: + -
• Then relational: < <= > >=
• Then equality: == !=
• Then logical AND &&, then logical OR ||
• Last: assignment = += -= *= /= %=

Example Without Parentheses

int a = 5, b = 10, c = 2;
int result = a + b * c;   // first b * c = 20, then a + 20 → 25

Example With Parentheses

int result = (a + b) * c; // first a + b = 15, then 15 * 2 → 30

Common Mistakes with Operators

• Using = instead of == in conditions.
• Dividing integers and expecting decimal results (use float or double).
• Forgetting that % only works with integers in standard C.
• Writing complex expressions with ++ and -- that are hard to understand.
• Not using parentheses and getting unexpected results due to precedence.

Practice Exercises (Try Yourself)

1. Simple Calculator: Write a program that reads two numbers and prints their sum, difference, product, quotient and remainder.
2. Range Check: Read an integer and check if it is between 1 and 100 (inclusive) using relational and logical operators.
3. Even or Odd: Use the modulus operator % to check whether a number is even or odd.
4. Attendance Eligibility: Input total working days and days present. If attendance percentage is greater than or equal to 75, print “Allowed for exam”, otherwise “Not allowed”.
5. Increment Demo: Write a small program that prints results of i++ and ++i step by step so you understand the difference.

Suggested Featured Image Concept

Use this description in your AI image tool to create a thumbnail for this lesson:

• A big blue “C” logo in the middle on a laptop screen.
• Around it, four groups of symbols:
  • “Arithmetic” with + - * / %
  • “Relational” with > < == !=
  • “Logical” with && || !
  • “Assignment” with = += -=
• A Tamil technician pointing to a flow showing: Values → Operators → Result.
• Title text at the top: “Operators in C” and subtitle: “Arithmetic, Relational, Logical & Assignment | Tamil Technicians”.