#include<stdio.h>.stdio.h, conio.h, math.h, ctype.h ,etc are the header files used in every C program at the beginning of programming. These types of header files are provided with compiler and cover the range of area as such as string, mathematical conversion, printing and reading of variable, etc.
#include<stdio.h> is called pre-processor directive and # is pre-processor operator. The definition of printf function is found in the header file stdio.h so #include<stdio.h> must be included in the beginning of the source code.
The header file conio.h must be included for the clrscr() function which clears the screen. Clrscrn is only used in turbo c++ compiler to clear the screen while on other compiler we use cls or clear to clear the screen.
.h is the extension for the header files. Every header files have .h extension. To search the compiler’s include directory for the specified files, we use angle bracket <>.