write 함수의 활용
while 반복문, if 조건문 활용
ex00 | ft_putchar.c
ex01 | ft_print_alphabet.c
ex02 | ft_print_reverse_alphabet.c
ex03 | ft_print_numbers.c
ex04 | ft_is_negative.c
ex05 | ft_print_comb.c
ex06 | ft_print_comb2.c
ex07 | ft_putnbr.c
ex08 | t_print_combn.c