There are 52 headers in the standard library;
Here is the reference
http://www.sron.net/softlist/catalog_13_softtime_desc_6.html
Http://william.cswiz.org/cppbook/ch1.pdf
Microsoft C standard library reference
http://msdn.microsoft.com/library/en-us/vcstdlib/html/vcoristandardclibraryReference.asp
MODERN C Design
http://www.jjhou.com/mcd-c-ch1-4.pdf