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Hello World

Beginner ~10 min read

It's time to write your first Lua program! Following the time-honored tradition of programming, we'll start with "Hello, World!"—a simple program that displays text on the screen. This lesson will introduce you to the print() function, comments, and the basic structure of a Lua program.

Your First Lua Program

Let's start with the simplest possible Lua program. Click "Run" to execute it:

Output 
Click Run to execute your code

Congratulations! You just ran your first Lua program! 🎉

How it works:
  • print() is a built-in function that outputs text to the console
  • Text inside quotes ("...") is called a string
  • Each statement in Lua is executed line by line, from top to bottom

The print() Function

The print() function is one of the most useful functions in Lua. It can print multiple values separated by commas:

Output 
Click Run to execute your code

Notice how print() automatically adds spaces between values and a newline at the end!

Feature Description Example
Single value Print one item print("Hello")
Multiple values Print several items print("A", "B", "C")
Numbers Print numeric values print(42, 3.14)
Mixed types Combine strings and numbers print("Age:", 25)
Pro Tip: You can print an empty line by calling print() with no arguments. This is useful for adding spacing in your output!

Comments in Lua

Comments are notes in your code that Lua ignores. They're essential for explaining what your code does, both for others and for your future self!

Single-Line Comments

Use two dashes (--) for single-line comments:

Output 
Click Run to execute your code

Multi-Line Comments

For longer comments spanning multiple lines, use --[[ to start and ]] to end: 

--[[
This is a multi-line comment.
It can span multiple lines.
Very useful for longer explanations!
]]

print("Comments are helpful!")
Best Practice: Write comments to explain why you're doing something, not what you're doing. The code itself should be clear enough to show what it does.

Good: -- Calculate tax for international orders
Bad: -- Multiply price by 0.15

String Basics

Strings are sequences of characters enclosed in quotes. Lua accepts both single and double quotes:

Output 
Click Run to execute your code
Escape Sequences: Use backslash (\) for special characters:
  • \n - New line
  • \t - Tab
  • \" - Double quote
  • \' - Single quote
  • \\ - Backslash

Common Mistakes

1. Forgetting quotes around strings

Wrong:

print(Hello)  -- Error: 'Hello' is not defined

Correct:

print("Hello")  -- Strings need quotes!

2. Mismatched quotes

Wrong:

print("Hello')  -- Quotes don't match!

Correct:

print("Hello")  -- Both double quotes
print('Hello')  -- Both single quotes

3. Forgetting parentheses

Wrong:

print "Hello"  -- This actually works in Lua!
                      -- But it's better to use parentheses

Correct:

print("Hello")  -- Always use parentheses for clarity
Note: Lua allows calling functions with a single string argument without parentheses (e.g., print "Hello"), but this is considered bad practice. Always use parentheses for consistency!

Exercise: Your Turn!

Task: Modify the code below to print information about yourself.

Requirements:

  • Print your name
  • Print your favorite programming language (Lua, of course! 😊)
  • Print your age or year you started learning programming
  • Add comments explaining each line
Output 
Click Run to execute your code
Show Solution 
-- Print my name
print("My name is Alice")

-- Print my favorite language
print("I love Lua!")

-- Print when I started programming
print("I started learning in 2024")

-- Print a fun fact
print("Fun fact: Lua means 'moon' in Portuguese! 🌙")

Summary

  • print(): Outputs text and values to the console
  • Strings: Text enclosed in quotes ("..." or '...')
  • Comments: Use -- for single-line, --[[ ]] for multi-line
  • Multiple values: Separate with commas in print()
  • Escape sequences: Use \n, \t, etc. for special characters

What's Next?

Great job! You've written your first Lua programs and learned the basics of output and comments. In the next lesson, we'll dive into Variables & Types—how to store and work with different kinds of data in Lua. This is where things get really interesting! 🚀

Previous Installation & Setup
Next Variables & Types