C Academy · Lesson

Arithmetic Operators

+, -, *, /, %.

Lesson 1 of 413 steps

Arithmetic Operators is a free C Academy lesson on CoddyKit. This is lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the C Academy learning path, and your progress syncs across the web and the CoddyKit app. The C Academy course includes 4 lessons in total.

Arithmetic in C

C gives you the everyday math operators you already know. They let you turn variables into expressions that compute new values.

+ addition
- subtraction
* multiplication
/ division
% modulo (remainder)

#include <stdio.h>
int main(void) {
    int a = 7, b = 3;
    printf("a + b = %d\n", a + b);
    printf("a - b = %d\n", a - b);
    return 0;
}

Multiplication

The * operator multiplies two values. The result type follows the operands, so two int values produce an int.

#include <stdio.h>
int main(void) {
    int width = 4, height = 5;
    int area = width * height;
    printf("Area = %d\n", area);
    return 0;
}

Integer Division

When both operands are integers, / performs integer division and discards the fractional part.

So 7 / 2 is 3, not 3.5.

#include <stdio.h>
int main(void) {
    int x = 7, y = 2;
    printf("7 / 2 = %d\n", x / y);
    return 0;
}

Floating Point Division

To keep the fractional part, make at least one operand a floating-point value. Then / performs real division.

#include <stdio.h>
int main(void) {
    double x = 7.0, y = 2.0;
    printf("7.0 / 2.0 = %.2f\n", x / y);
    return 0;
}

The Modulo Operator

The % operator gives the remainder of integer division. It only works with integer operands.

7 % 3 is 1 because 7 = 2*3 + 1.

#include <stdio.h>
int main(void) {
    printf("7 %% 3 = %d\n", 7 % 3);
    printf("10 %% 5 = %d\n", 10 % 5);
    return 0;
}

Modulo Use Case: Even or Odd

A common trick: a number is even when n % 2 == 0, and odd otherwise.

#include <stdio.h>
int main(void) {
    int n = 9;
    if (n % 2 == 0)
        printf("%d is even\n", n);
    else
        printf("%d is odd\n", n);
    return 0;
}

Unary Minus

The - operator also works as a unary operator to negate a value.

#include <stdio.h>
int main(void) {
    int temp = 5;
    printf("Negated: %d\n", -temp);
    return 0;
}

Mixing int and double

When you mix types, C promotes the int to double before computing. This is called type promotion.

#include <stdio.h>
int main(void) {
    int a = 5;
    double b = 2.0;
    printf("Result = %.2f\n", a / b);
    return 0;
}

Division by Zero

Integer division or modulo by zero is undefined behavior in C and usually crashes the program. Always guard against a zero divisor.

#include <stdio.h>
int main(void) {
    int n = 10, d = 0;
    if (d != 0)
        printf("%d\n", n / d);
    else
        printf("Cannot divide by zero\n");
    return 0;
}

Combining Operators

You can chain operators to build larger expressions. C evaluates them according to precedence rules you will study soon.

#include <stdio.h>
int main(void) {
    int total = 2 + 3 * 4 - 1;
    printf("total = %d\n", total);
    return 0;
}

A Small Calculator

Putting it together: read two values into variables and print several arithmetic results at once.

#include <stdio.h>
int main(void) {
    int a = 12, b = 5;
    printf("Sum: %d\n", a + b);
    printf("Diff: %d\n", a - b);
    printf("Quot: %d\n", a / b);
    printf("Rem: %d\n", a % b);
    return 0;
}

Quick Check

Test your understanding of arithmetic operators.

Answer it in the interactive lesson

Recap: Arithmetic Operators

You learned the five arithmetic operators in C.

+ - * behave as expected
/ truncates for integers but gives real results with floats
% gives the remainder and is integer-only
Mixing types promotes to the wider type
Never divide by zero

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Frequently Asked Questions

Is the “Arithmetic Operators” lesson free?

Yes — the full text of “Arithmetic Operators” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the C Academy course, upgrade to CoddyKit PRO. The C Academy course includes 4 lessons in total.

What will I learn in “Arithmetic Operators”?

+, -, *, /, %. You practise C Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start C Academy?

No prior experience is required. C Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 1 of 4.

How long does the “Arithmetic Operators” lesson take?

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