about the C Library
 

does anyone know is there a book or something else telling about the C Library,like telling about the kernel.because I want to know when I call read,how does it happen?the OS just provide the system calls interface,
the C Library above it call the system calls to implement.And I find it is hard to read the C Library source code(glibc).so ......
Forthermore,where the linux acheive the POSX thread,in the kernel sapce or totally in the user-sapce,when I use pthread_create twice in my main and when I ps ax,I found four,why does not three???

Yeah.

Herbert Schildt 'C The Complete Reference' has all of the library calls fully documented with simple examples.

Kelly & Pohl 'A Book On C' shows you how to program and not make a lot of beginner errors.
It covers the use of a lot of the standard library.

I've been writing C code since 1978 and I sometimes look up function prototypes for standard library calls I need to use - about once every six years. In other words, you only need to know that fmodf() exists, and what it does --- not everything about it.