Tradition dictates that the first program that is written in any programming language should be Hello, World! In that same spirit, let's look at the "hello world" of Bitsy: Passthrough:
.. literalinclude:: examples/passthrough.bitsy :language: bitsy :linenos:
We see a module declaration, mod Passthrough. Inside, we see two ports, one incoming port named out and one outgoing port named in. Both have type Word[8], meaning that an 8-bit value passes across them. The line out := in connects the input port in to the output port out. The notation := is called a wire.