| Standard Library Header File | Explanation |
| cassert | Contains macros and information for adding diagnostics that aid program debugging |
| cctype | Contains function prototypes for functions that test characters for certain properties, and function prototypes that can be used to convert lowercase to uppercase and vice versa. |
| cfloat | Contains the floating point size limits of the system. |
| climits | Contains the integral size limits of the system. |
| clocale | Contains function prototypes and other information that enables a program to be modified for the current locale on which it is running. |
| cmath | Contains function prototypes for the math library functions. |
| cstdlib | Contains function prototypes for conversion of numbers to text and text to numbers, memory allocation, random numbers, and other utility functions. |
| cstring | Contains function prototypes for string processing functions using C-style strings. |
| ctime | Contains function prototypes and types for manipulating the time and date. |