Basic Program Structure

Part of the Fundamentals section of Coddy's Rust journey — lesson 4 of 75.

In Rust, every executable program starts with the main function. This function is the entry point of the program, and it's where the execution begins.

The main function is defined using the fn keyword followed by main and a pair of parentheses (). The code to be executed is placed within curly braces {}.

Here's a simple breakdown of a basic Rust program:

fn main() { // Main function
    println!("Hello, Coddy!"); // Output statement
}

Important note: In Rust, each statement must end with a semicolon (;). The semicolon is mandatory and tells Rust that you've reached the end of a statement.

Forgetting to add a semicolon will result in a compilation error. However, note that code blocks enclosed in curly braces {} (like function declarations) don't need semicolons.

Challenge

Beginner

Create a Rust program that contains the main function. Inside the main function, write code to output the following text:

This is my first Rust program!

Cheat sheet

Every Rust program starts with the main function, which is the entry point where execution begins:

fn main() {
    println!("Hello, Coddy!");
}

Key points:

Use fn keyword to define functions
Code goes inside curly braces {}
Each statement must end with a semicolon ;
Use println!() to output text to the console

Try it yourself

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

Rust Hello World!CommentsBasic Program Structure

4Operators Part 1

Arithmetic Operators Modulo Operator Arithmetic Shortcuts Comparison Operators String Comparison

7Basic IO

Printing to Console Reading User Input Recap - Till 120 Recap - True or False

10Variable Bindings

Scope Shadowing Part 1 Variable Binding Shadowing Part 2

13Arrays Continued

Mutable Reference Arrays Array Methods Recap - Product Array Recap - Reversed Array Better Print

16Final Projects

Number Pattern Pattern Finder Student Grade Calculator

2Variables Part 1

Numbers Char String Boolean Mutable Variables

5Operators Part 2

Logical Operators Part 1 Logical Operators Part 2 Recap - Simple Logic Logical Operators Part 3

8Calculator App

Welcome Message Getting Numbers

Basic Operations

Formatted Output

11Functions

Declaring Functions Parameters and Arguments Return Values Multiple Return Values Recap - Sigma Function Recap - Validation Function

14Iterating Over Arrays

Range Guide Enhanced For Loop Borrow In Loop Common Array Operations

3Variables Part 2

Type Declaration Naming Conventions Type Inference Recap - Initialize Variables Type Casting

6Decision Making

If Expressions If-Else Match Statement Recap - If Else Nested If - Else

9Loops

For Over Series While Loop Break Continue Nested Loop Loop Labels Infinite Loop Recap - Dynamic Input

12Arrays Basics

Declaring Arrays Array as Parameter Accessing Elements Modifying Arrays Recap - Pretty Print Array

15String Operations

String Methods format! Macro String Conversion Recap - Format