File 0-puts_recursion.c is a function that prints a string, followed by a new line.
File 1-print_rev_recursion.c is a function that prints a string in reverse.
File 2-strlen_recursion.c is a function that returns the length of a string.
File 3-factorial.c is a function that returns the factorial of a given number.
File 4-pow_recursion.c is a function that returns the value of x raised to the power of y.
File 5-sqrt_recursion.c is a function that returns the natural square root of a number.
File 6-is_prime_number.c is a function that returns 1 if the input integer is a prime number, otherwise return 0.
File 7-is_palindrome.c is a function that returns 1 if a string is a palindrome and 0 if not.
File 100-wildcmp.c is a function that compares two strings and returns 1 if the strings can be considered identical, otherwise return 0. It uses the concept of wildcards.
File _putchar.c is a file containing the _putchar function.
File main.h is the header file containing the function prototypes