2. Hello world#

Think of writing your first program as saying your first word. It’s a profound moment, a starting point for countless conversations with your computer. In programming, that first word is usually ‘Hello, World!’. Here’s the gist of that program:

Console.WriteLine("Hello, World!");

If we run that program, here’s what we get:

Hello, World!

../_images/cover-hello-world.jpg — Fig. 2.1 Like a rocket ready to launch, ‘Hello World’ is the program that propels you into the wonderfully powerful world of coding. Life will never be the same again.#

To be able to write this monumental program we must first decide where we’re going to write and execute our code. We usually refer to this as what ‘development environment’ we’re using.

If you’re completely new to coding I recommend that you use the online environment Replit but we’ll also outline the basics steps for if you want to use ‘Visual Studio Code’ (also known as VS Code), or ‘Visual Studio’ as well.

Getting started with Replit#

Note

Coming soon.

Getting started with Visual Studio Code#

Note

Coming soon.

Getting started with Visual studio#

Here’s a quick overview of how to get started using the program Microsft Visual Studio. This is an application that you have to download and run on your own computer.

Warning

Microsoft will drop support for Visual Studio on Mac so it is not advisable to learn Visual Studio if you’re on a Mac.

Note

More detailed instructions can be found in a tutorial published by Microsoft.

Download and install Visual Studio.
Open Visual Studio and select ‘Create a new project’.
In the project template screen, select ‘Console App (.NET)’ and click ‘Next’.
Give your ‘Project’ and ‘Solution’ a name (such as ‘Hello World’), choose a location to save your project, and click ‘Next’.
Ensure that the target framework is .NET 7.0 and ‘Do not use top-level statements’ is unchecked. Then, click ‘Create’.
After the project is created, you’ll see a file named Program.cs opened in the editor with the following lines:
```
// See https://aka.ms/new-console-template for more information
Console.WriteLine("Hello, World!");
```
Run your program by clicking the green ‘Play’ button in the top or using the shortcut Cmd+Enter on Mac or F5 on Windows. Alternatively, you can navigate to Debug > Start Debugging in the top menu.
Verify that the output you get is:
```
Hello, World!
```

Note

If you find that the terminal window opens and immediately closes after running your program, it’s because your terminal is set to close when the program finishes executing. The simplest workaround is to add Console.ReadKey(); on a new last line of the file.

This extra line of code tells your program to wait for a keypress before closing the terminal window, which causes the window to remain open.

Running your first program#

When you’re pressing the ‘Play’ button in your development environment your code is compiled into a language that your computer understands and then executes it. Don’t worry about the details for now, we’ll explain what all this means in the coming chapters.

If you’ve got lines starting with two forward slashes (//) then these are comments. Comments are like notes for programmers and these are ignored by the compiler. We’ll talk more about this later.

If you’ve got lines starting with the word using then this is an import which makes additional types available to your program. In this case it makes it possible for us to use the Console class. We’ll explain this later on so don’t worry about this line now but keep it in.

The line that reads Console.WriteLine("Hello world"); is however a statement. It calls the static WriteLine method of the Console class, passing the string value "Hello, World!", which causes that message to be printed to the terminal.

This is your first program! Hooray. Let’s run it by pressing the ‘Play’ button.

Console.WriteLine("Hello, World!");

Hello, World!

Conclusion#

Congratulations on writing and running your first program! This might feel like a small step, but it’s the start of a grand journey into the wonderfully powerful world of programming. Your life is never going to be the same again. In the next chapter, we’ll begin to uncover the magic that transforms your code into an application your computer can run. Exciting times ahead!

Exercise

Currently, your program prints Hello, World!. Can you change the program so that it prints a different message of your choice? Maybe Hello, my name is <your name>..