Hello World

[Swift](https://developer.apple.com/swift) is a powerful and intuitive general-purpose programming language developed by Apple. Its development started in July 2010.

Much of the inspiration for Swift came from languages like Objective-C, Rust, Haskell, Ruby, Python, C#, and many others. Swift's concise yet expressive syntax and modern features make it the perfect first language for beginners and one experienced developers enjoy transitioning into. 

Its first version was released in 2014 with the intent to create applications for: 

- 📱 iOS
- ⌚ watchOS
- 🖥️ macOS
- 📺 tvOS
- 🐧 Linux

Since then, hundreds of companies including Uber and Slack have incorporated Swift into their tech stack.

In this lesson, we’ll start by learning the basic concepts and fundamentals of Swift. 

Happy coding!

Introduction to Swift

Our own code can quickly become difficult to understand when we return to it — sometimes only a few hours later! For this reason, it’s often useful to leave a note or reminder in our code for our future selves or other developers.

Comments can explain what the code is doing, leave instructions for developers using the code, or add any other useful annotations.

There are two types of code comments in Swift:

- *A single line comment* will comment out a single line and is denoted by two forward slashes `//` preceding it:
```swift
// Prints "hi"
print("hi")
```
You can also use a single line comment after a line of code:
```swift
print("hi")  // Prints "hi"
```

- A *multiline comment* will comment out multiple lines and is denoted by `/*` to begin the comment, and `*/` to end the comment:
```swift
/* This is all commented out.
print("hi")
None of this is going to run! */
```


Comments

We learned how to output a line of text with the following code:

```swift
print("🚙💨")
```

It will output:

```bash
🚙💨
```

We can also output multiple lines by adding more [`print()`](https://developer.apple.com/documentation/swift/1541053-print) statements:

```swift
print("Hello")
print("Goodbye")
```

This will output:

```bash
Hello
Goodbye
```

Notice how the order of the printed statements matches the order of our code. That's because Swift code is read from top to bottom.

Now let’s use what we learned so far to complete a coding challenge.

Print

Take a look at the **Hello.swift** file in the code editor that is placed in the middle of the screen. It's a Swift program!

When learning a new language, tradition suggests that our first program prints to the screen: `Hello, world!`.

In Swift, this can be done in a single line:

```swift
print("Hello, world!")
```

Everything inside the double quotes will be printed to the terminal. 

The _terminal_ is a window that allows people to interact with a computer program. The terminal is the black panel on the right. It should be blank right now, but we'll change that in a moment.

**Note:** Don't worry if you don't understand something, everything introduced in this lesson is explained in the rest of this course.

Woohoo! You have written a few Swift programs. 🙌

In this lesson, you have learned:

- Swift is a general-purpose coding language.
- The code is read from top to bottom.
- `print()` is used to output to the terminal:

```swift
print("This... is... fun.")
```
- Single line comments are created using `//`.
- Multiline comments are created using `/*` `*/`.