File 0-sum_them_all.c is a function that returns the sum of all its parameters.

File 1-print_numbers.c is a function that prints numbers, followed by a new line.

File 2-print_strings.c is a function that prints strings, followed by a new line.

File 3-print_all.c is a function that prints anything.

File variadic_functions.h is the header file that contains all the function prototypes.