Variables & Data — Storing Information

Now that you can print output, let's learn how to store and manipulate data using variables.

What Is a Variable?

A variable is a named box that holds a value. You can put data in, take it out, or replace it.

let name = "Alice";    // Put "Alice" in the box named 'name'
let age = 25;          // Put 25 in the box named 'age'
let height = 5.75;     // Put 5.75 in the box named 'height'
let is_student = true; // Put true in the box named 'is_student'

In AdeshLang, use let to create a variable:

let variable_name = value;

Variable Names

Follow these rules for names:

Rule	Example
Start with letter or _	name, _count, user1
Can contain letters, numbers, _	user_name, count2, _private
Case-sensitive	name ≠ Name ≠ NAME
Can't use keywords	❌ let, if, else, fn, class

Good names:

let user_name = "Alice";
let max_score = 100;
let is_active = true;
let _temp = 42;

Bad names:

let 2names = "Bob";      // ❌ Starts with number
let user-name = "Bob";   // ❌ Hyphen not allowed
let let = 10;            // ❌ 'let' is a keyword

Basic Types

AdeshLang infers the type from the value:

let whole_number = 42;        // number (integer)
let decimal = 3.14;           // number (float)
let text = "Hello, World!";   // string
let yes = true;               // boolean
let no = false;               // boolean
let nothing = null;           // null (empty value)

Check the type with typeof:

let x = 42;
print(typeof x);     // "number"

let name = "Alice";
print(typeof name);  // "string"

let flag = true;
print(typeof flag);  // "boolean"

Output:

number
string
boolean

Reassignment — Changing Values

In AdeshLang, variables are mutable by default — just assign a new value:

let score = 0;
print("Score:", score);    // Score: 0

score = 10;
print("Score:", score);    // Score: 10

score = score + 5;
print("Score:", score);    // Score: 15

Output:

Score: 0
Score: 10
Score: 15

No mut keyword needed! Just use = to update.

Arithmetic Operations

let a = 10;
let b = 3;

print("Add:", a + b);       // 13
print("Subtract:", a - b);  // 7
print("Multiply:", a * b);  // 30
print("Divide:", a / b);    // 3.333...
print("Modulo:", a % b);    // 1 (remainder)

Output:

Add: 13
Subtract: 7
Multiply: 30
Divide: 3.3333333333333335
Modulo: 1

String Operations

let first = "Hello";
let last = "World";

print(first + " " + last);    // Hello World
print(first + ", " + last);   // Hello, World

// String length
let word = "AdeshLang";
print("Length:", len(word));  // Length: 9

Output:

Hello World
Hello, World
Length: 9

Collections: Arrays and Objects

Arrays — Ordered Lists

let numbers = [1, 2, 3, 4, 5];
let names = ["Alice", "Bob", "Charlie"];
let mixed = [1, "two", true, 3.14];

print("First:", numbers[0]);        // First: 1 (index 0)
print("Length:", len(numbers));     // Length: 5

// Add to end
numbers.push(6);
print(numbers);                     // [1, 2, 3, 4, 5, 6]

Output:

First: 1
Length: 5
[1, 2, 3, 4, 5, 6]

Objects — Key-Value Pairs

let person = {
    name: "Alice",
    age: 25,
    city: "New York"
};

print("Name:", person.name);        // Name: Alice
print("Age:", person.age);          // Age: 25

// Add/modify properties
person.email = "alice@example.com";
person.age = 26;

print(person);                      // { name: "Alice", age: 26, city: "New York", email: "alice@example.com" }

Output:

Name: Alice
Age: 25
{ name: "Alice", age: 26, city: "New York", email: "alice@example.com" }

Practice Exercise

Create a file profile.adesh and build a user profile:

// 1. Create variables for your info
let my_name = "Your Name";
let my_age = 20;
let my_height = 5.8;
let is_coder = true;

// 2. Create an array of your hobbies
let hobbies = ["coding", "reading", "gaming"];

// 3. Create an object for your favorites
let favorites = {
    color: "blue",
    food: "pizza",
    language: "AdeshLang"
};

// 4. Print everything nicely
print("=== MY PROFILE ===");
print("Name:", my_name);
print("Age:", my_age);
print("Height:", my_height);
print("Coder?", is_coder);
print("");
print("Hobbies:", hobbies);
print("Favorites:", favorites);

Output:

=== MY PROFILE ===
Name: Your Name
Age: 20
Height: 5.8
Coder? true

Hobbies: [coding, reading, gaming]
Favorites: { color: "blue", food: "pizza", language: "AdeshLang" }

Run it:

adesh run profile.adesh

Common Mistakes

Mistake	Error	Fix
Using variable before declaring	x is not defined	Add let x = ... first
Typo in variable name	name is not defined	Check spelling: my_name vs my_nmae
Forgetting quotes on string	Unexpected token	Use "text" not text
Using = instead of == in condition	Logic bug	= assigns, == compares

Summary

✅ You learned:

• let name = value creates a variable
• Variables are mutable by default — just reassign with =
• Basic types: number, string, boolean, null
• typeof reveals the type
• Arrays [] for lists, Objects {} for key-value data
• len() gives array/string length

Next Step

Now let's meet the operators that compute with our values! Continue to Operators & Expressions →