0The process of calling a function by itself is called recursion and the function which calls itself is called recursive function.
Syntax of Recursive Function
returntype recursive_func ([argument list])
{
statements;
... ... ...
recursive_func ([actual argument]);
... ... ...
}
Example:- C Program to show infinite recursive function
#include
int main()
{
printf("Hello world");
main();
return 0;
} 
