1. stdio.h This header file defines types and macros needed for the standard I/O package.
2. string.h This header file declares various string manipulation and memory manipulation routines.
3. math.h This header file declares various math functions and math error handlers.
4. stdlib.h This header file declares several commonly used routines like conversion routines,search/sort routines, and other miscellaneous things.
5. iostream.h This header file declares basic C++ stream I/O routines.
6. iomanip.h This header file declares stream I/O manipulators and contains macros for creating parameterised manipulators
