Variables and Data Types

A useful program must be able to store data. In AHA! Lang, we store data in variables — named containers that hold values.

Creating Variables with let

let umur = 25;
let nama = "Budi";
let sudah_lulus = true;

The basic pattern:

let <name> = <value>;

• let is the keyword for declaring a variable.
• <name> is a name you choose yourself.
• <value> is the data you want to store.

Basic Data Types

Every value in AHA! Lang has a type — a category of data that determines what can be done with it:

Important: you don't need to write the type when declaring — the compiler infers it from the value. This is called type inference.

Displaying a Variable's Value

let umur = 25;

print(umur);           // 25 — an Int variable
print_str("Umur: ");   // Umur:

Naming Rules

Variable names can use letters, numbers, and the underscore _:

• Allowed: umur, my_var2, _private
• Not allowed: 2umur (starts with a number), umur 2 (contains a space)
• Avoid names identical to keywords like if, let, while — they have special meaning in AHA!

Use clear and descriptive names. total_belanja is far better than x if what you're storing is a shopping total.

Changing a Variable's Value

Unlike some other languages where let is immutable, in AHA! Lang a variable can be changed with the assignment operator =:

let skor = 10;
print(skor); // 10

skor = 15;   // change its value
print(skor); // 15

skor = skor + 5; // read the old value, compute, store the new one
print(skor);     // 20

How to read skor = skor + 5;:

1. Take the old value of skor (10).
2. Add 5 → 15.
3. Store the result back into skor.

This pattern of incrementing a value is very common — you'll often see it alongside loops.

Variables Inside Expressions

Variables can be used anywhere a value is needed:

let harga = 15000;
let jumlah = 3;
let total = harga * jumlah;

print(total); // 45000

Exercises

1. Create a variable kampus holding the name of your campus, then print it with print_str.
2. Create two variables a = 8 and b = 12, then print the results of a + b, a * b, and b - a.
3. Create a variable counter = 0, add 1 three times (without changing the 0 on the first line), then print its value.

On to Operators and Expressions