Variables & Types

What you’ll learn

• Name values, calculate results, and print your first answer.

The concept

A variable is a name attached to a value. Start by naming each piece of information your program needs, then write an expression that combines those values. Python determines a value’s type at runtime; Java asks you to declare a variable’s type, such as int for whole numbers. Both languages support addition, subtraction, multiplication, and parentheses. Choose descriptive names like packs rather than mysterious letters. An assignment stores a result; it does not create a permanent mathematical equation. If a value changes later, an earlier calculation is not automatically repeated. In these examples, sample data is written directly in the program so you can run it immediately. Change one number, predict the new output, and run the code again. That prediction-and-check habit is the foundation of debugging.

Worked example

public class Main {
    public static void main(String[] args) {
        int packs = 4;
        int perPack = 6;
        int given = 5;
        int remaining = packs * perPack - given;
        System.out.println(remaining);
    }
}

Try thinking it through

Sticker inventory

A club has 4 packs with 6 stickers in each pack. It gives away 5 stickers. Calculate and print the number left.

Example input

packs = 4, per_pack = 6, given = 5

Expected output

19

Ready to try it yourself?

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