There are lots of header files, so there seems a lot to memorize. Don't. Learn the basics as you go (buy that book). The rest is experiance. And there is no shame in reading a reference if you don't know something, or need to know a little extra.
The "std" stands for "standard" indeed. In C++ the current standard (we are talking about the international standard as defined by the ISO comittee) requires to define the standard within the namespace std.
A few rules for the current standard:
- Name C++ headers without the .h extension: <iostream> instead of <iostream.h>
- Old C headers precede with a "c" without the .h extension: <cmath> instead of <math.h> or <math>.
That's right, functions, members and so forth are grouped and defined in specific header files. Here is a picture:
