The simplest way to read an txt file and display it/write it to another file ?

Hi,
Could you tell me what's the simplest way to display a file
at the GTM> prompt ? And how can I rewrite it to another
one ?

Moreover I have strong difficulties to understand the syntax
of M, in particular in many example I see things like
~         set ...
~         use ...
~         <other instructions>
~         <etc.>
~THING1
~         for ...
~         <some instr.>
~THING2
~         while...
~         <etc etc.>
When I see this does it mean this is the contents of a
..m file (the first line and following begin with blank spaces,
the a section starts with a string, then the following lines
again are with spaces, then another section starts at the
beginning etc.) ? (I've used the '~' to signify it's the beginning
of my line)
If I start typing at the mumps prompt like above, it fails (that's
why I guess such examples represent the contents of M files
don't they ?)...

Thanks.
S=E9bastien