user18790: So this is a question not just about the #include  but most all includes you find while programming in C. 
So I understand a library is prewritten code and when you include that library are you able to used certain function that are included in that library. 
What I have always wanted to know is: where can you find the "instruction set", in C, for these libraries?
How can I find out what commands are available for me to use with this library?
hope this makes sense.
thank you everyone.

user10794: 
What I have always wanted to know is: where can you find the "instruction set", inc C, for these libraries?

The libraries are usually found in the libraries sub-folder under your sketchbook folder (wherever that is). There is also another libraries folder inside the IDE install folder for the "official libraries".

How can I find out what commands are available for me to use with this library?

Usually the library documents them in one way or another. Try looking inside the .h file used by the library to see what functions are exposed.

18790: <p>So this is a question not just about the #include  but most all includes you find while programming in C. </p>

<p>So I understand a library is prewritten code and when you include that library are you able to used certain function that are included in that library. </p>

<p>What I have always wanted to know is: where can you find the "instruction set", in C, for these libraries?</p>

<p>How can I find out what commands are available for me to use with this library?</p>

<p>hope this makes sense.</p>

<p>thank you everyone.</p>
 10794: <blockquote>
  <p>What I have always wanted to know is: where can you find the "instruction set", inc C, for these libraries?</p>
</blockquote>

<p>The libraries are usually found in the <code>libraries</code> sub-folder under your sketchbook folder (wherever that is). There is also another <code>libraries</code> folder inside the IDE install folder for the "official libraries".</p>

<blockquote>
  <p>How can I find out what commands are available for me to use with this library?</p>
</blockquote>

<p>Usually the library documents them in one way or another. Try looking inside the <code>.h</code> file used by the library to see what functions are exposed.</p>
