Commands are not always available. A lot of complexity in programming is because
the set of commands available on Linux, Windows and OSX differ. For example
`ls` is not available on Windows by default. On Windows we have a command `dir`
which performs similar function.
To further complicate things, even if the commands are available they sometimes
differ. Desipite these complications, they are not so bad, and are essential if
you want to use the machine you have at the fullest.
Writing command line applications are easier than building user interfaces so
you will find a lot of functionalities are distributed as command line programs
only, and not as GUI software you may be been used to so far.
We have written a mini [guide on command commands: `fastn.com/cmds/`](/cmds/)
you would want to use on a day to day basis which going through this book.
Familiarise yourself with them, and come back to them on need basis. But do not
bother too much about not knowing these commands or memorising them, they are
best learnt incrementally, on a need to know basis, and we will be gradually
learning about the commands you need while you are reading this book.
Go on, issue the command `ls` or `dir` depending on which platform you are on.
You will have to write the words `ls` or `dir` in the terminal or command prompt