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Part 01 - Starting Out

Boo is an amazing language that combines the syntactic sugar of Python, the features of Ruby, and the speed and safety of C#.

Like C#, Boo is a statically-typed language, which means that types are important. This adds a degree of safety that Python and other dynamically-typed languages do not currently provide.

It fakes being a dynamically-typed language by inference. This makes it seem much like Python's simple and programmer-friendly syntax.


Hello, World!

A Hello, World! program is very simple in Boo.
Don't worry if you don't understand it, I'll go through it one step at a time.
Hello, World!
Hello, World!
  1. First, you must compile the file to an executable.
    1. Open up a new command line
    2. cd into the directory where you placed the file.
    3. booc (this assumes that Boo is installed and in your system path)
    4. helloworld.exe
      OR, if you are using Mono,
    5. mono helloworld.exe
  2. Using the print macro, it prints the string "Hello, World!" to the screen.
  3. Using the print function, it prints the string "Hello, World!" to the screen.

Now these both in the end, do the same thing. They both call System.Console.WriteLine("Hello, World") from the .NET Standard Library.



Using the macro version (print "Hello, World!") is recommended.

And it's that simple.

Comparing code between Boo, C#, and VB.NET

Now you may be wondering how Boo could be as fast as C# or VB.NET.
Using their Hello World programs, I'll show you.

Boo Output
Hello, World!
C# Output
Hello, World!
VB.NET Output
Hello, World!

All three have the same end result and all three are run in the .NET Framework.
All three are first translated into MSIL, then into executable files.

If you were to take the executables created by their compilers, and disassemble them with ildasm.exe, you would see a very similar end result, which means that the executables themselves are very similar, so the speed between C# and Boo is practically the same, it just takes less time to write the Boo code.


booish is a command line utility that provides a realtime environment to code boo in. It is great for testing purposes, and I recommend following along for the next few pages by trying out a few things in booish.

You can invoke it by loading up a terminal, then typing booish (this assumes that Boo is installed and in your system path), or by double-clicking the booish icon. In booish, you can up arrow to re-enter (with editing) a previously entered line.

Here's what booish will look like:

>>> print "Hello, World!"
Hello, World!


  1. Write a Boo program that prints "Hello, World!", then prints "Goodbye, World!"
  2. Play around with booish
  3. Advanced: Compile the Hello, World! programs for Boo (using booc) and C# (using csc or mcs), run ildasm on each of them and compare the result.

Go on to Part 02 - Variables

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