stdio.h

conio.h

string.h

stdlib.h

math.h

This is a standard input/output header file. It contains all the library functions regarding standard input/output.

This is a console input/output header file.

It contains all string related library functions like gets(), puts(),etc.

This header file contains all the general library functions like malloc(), calloc(), exit(), etc.

This header file contains all the math operations related functions like sqrt(), pow(), etc.