C# Academy · Lesson

Arithmetic and Assignment Operators

Use +, -, *, /, % and compound assignment forms.

Arithmetic and Assignment Operators is a free C# Academy lesson on CoddyKit — 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, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Arithmetic Operators

C# gives you the classic math operators: + add, - subtract, * multiply, / divide, and % remainder (modulo).

They work on numeric types like int, long, double, and decimal.

using System;

class Program {
    static void Main() {
        int a = 10, b = 3;
        Console.WriteLine(a + b);
        Console.WriteLine(a - b);
        Console.WriteLine(a * b);
    }
}

Integer Division

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

10 / 3 is 3, not 3.33.

using System;

class Program {
    static void Main() {
        int result = 10 / 3;
        Console.WriteLine(result);
        Console.WriteLine(7 / 2);
    }
}

Floating-Point Division

To keep the fraction, make at least one operand a floating-point type, such as double. You can add .0 or cast.

using System;

class Program {
    static void Main() {
        double r1 = 10.0 / 3;
        Console.WriteLine(r1);
        double r2 = (double)7 / 2;
        Console.WriteLine(r2);
    }
}

The Modulo Operator

The % operator returns the remainder after division. It is great for checking even/odd or cycling values.

using System;

class Program {
    static void Main() {
        Console.WriteLine(10 % 3);
        Console.WriteLine(8 % 2);
        Console.WriteLine(7 % 4);
    }
}

Even or Odd with Modulo

A number is even when n % 2 == 0. This is the most common use of modulo.

using System;

class Program {
    static void Main() {
        for (int n = 1; n <= 5; n++) {
            string kind = (n % 2 == 0) ? "even" : "odd";
            Console.WriteLine(n + " is " + kind);
        }
    }
}

Operator Order in Expressions

C# follows math precedence: *, /, and % happen before + and -. Use parentheses to be explicit.

using System;

class Program {
    static void Main() {
        Console.WriteLine(2 + 3 * 4);
        Console.WriteLine((2 + 3) * 4);
    }
}

Compound Assignment: +=

Compound assignment combines an operation with assignment. x += 5 is shorthand for x = x + 5.

using System;

class Program {
    static void Main() {
        int score = 10;
        score += 5;
        Console.WriteLine(score);
        score += 20;
        Console.WriteLine(score);
    }
}

Compound Assignment: -= and *=

The same pattern works for every arithmetic operator. x -= 2 subtracts, x *= 3 multiplies in place.

using System;

class Program {
    static void Main() {
        int x = 20;
        x -= 5;
        Console.WriteLine(x);
        x *= 2;
        Console.WriteLine(x);
    }
}

Compound Assignment: /= and %=

/= divides and assigns, %= takes the remainder and assigns. They follow the same integer/floating rules as the base operators.

using System;

class Program {
    static void Main() {
        int y = 100;
        y /= 4;
        Console.WriteLine(y);
        y %= 7;
        Console.WriteLine(y);
    }
}

Increment and Decrement

++ adds one, -- subtracts one. Prefix (++x) changes the value before use; postfix (x++) after use.

using System;

class Program {
    static void Main() {
        int i = 5;
        Console.WriteLine(i++);
        Console.WriteLine(i);
        Console.WriteLine(++i);
    }
}

Building a Running Total

Compound assignment shines in loops where you accumulate a value.

using System;

class Program {
    static void Main() {
        int total = 0;
        for (int n = 1; n <= 5; n++) {
            total += n;
        }
        Console.WriteLine("Sum 1..5 = " + total);
    }
}

Quick Check

Test your understanding of arithmetic and compound assignment.

Recap

You learned the C# arithmetic operators + - * / %, that integer division truncates while floating-point division keeps the fraction, and that modulo gives the remainder.

Compound assignment (+= -= *= /= %=) updates a variable in place, and ++/-- step by one. These tools power counters and running totals.

Frequently asked questions

Is the “Arithmetic and Assignment Operators” lesson free?

Yes — the full text of “Arithmetic and Assignment Operators” is free to read here on the web, and the C# Academy course includes 4 lessons in total. 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.

What will I learn in “Arithmetic and Assignment Operators”?

Use +, -, *, /, % and compound assignment forms. 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; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Arithmetic and Assignment Operators” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this C# Academy lesson?

Yes. Every C# Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

← Back to C# Academy