In the first generation of computer programming, there were manufacturer's manuals. You read them, you studied them, you figured out how to program the computer. (One of my consulting friends had a great story about not even having these machine manuals. I must tell you about it some day...)
In the second generation, everyone also had a few good books about programming. Otherwise: we relied on those manufacturer's manuals.
In the third generation: everyone had about ten books on programming, but if you needed to figure out how to do soomething useful, you consulted your guru. Every programming staff had a few gurus (to cover many different topics), and you couldn't live without them.
In the fourth generation -- the present, that is -- everyone has at least twenty books on programming. But routinely, to figure out how to do something useful, we search the web.
A weeks ago, I needed to write a program -- right now, right this minute! -- to convert video in YUV 420 format, to YVU 422 format. In my opinion, after running all the usual web searches, YVU 422 is rather ambiguous, it has too many permissible forms. In any case, the video was not displaying correctly, I obviously had not figured out the format. At about 9 PM (EDT) I found myself hitting the telephone. Whom could I call right now who would know more about video than I? It was Guru Time, a great nostalgic throwback to the third generation of computer programming. My Gurus came through for me, too.