[Boost-build] Locating a Boost build command

Subject: [Boost-build] Locating a Boost build command
From: Edward Diener (eldiener_at_[hidden])
Date: 2015-08-19 15:03:35

I see in a current Boost build jamfile ( libs\context\build\Jamfile.v2 ) 
that the command 'cpp' is being invoked for a particular action. Is 
'cpp' a built-in command ? If so where would I find its explanation, or 
where would I find explanations for any built-in commands ?