Guide Program 3

Harold Grovesteen

I have just committed Guide Program 3 (and its associated samples
directory) to the SATK repository.

Program 3 is another version of Hello World.  The big difference from
the previous two programs is that the message is delivered using I/O.
 The program is a bit more complex and there is a lot more explanation
of how the program works to go along with it.

How the IPL channel program operates is also described in Program 3,
Step 2.

One of the challenges I have had in writing documentation is describing
how channel I/O operates.  I am thinking that a description for
programmers, as opposed to a description for hardware engineers, might
be appropriate.  Let me know what you think, please.

Harold Grovesteen