The C standard library offers quite a bit of functionality. The first thing to be aware of when using any part of this library is what's in it. The following tables provide the header filenames and descriptions of the functions prototyped in each header file.
The following table shows the library files before C99:
| Filename | Description |
| alloca.h | Non-standard |
| assert.h | Contains the assert macro, used to assist with detecting logical errors and other types of bugs in debugging versions of a program |
| ctype.h | Defines a set of functions used to classify characters by their types... |
