Using write function to display pointer

I wrote the attached code with the intention to get 42 as the output but I instead get an asterisks (*) I know that 42 is the ACII value of an asterisk. Please look at my code and see something I might have missed. The program is in C using the <unistd.h> library, I have to use the unistd.h and not the stdio.h for this code.

[code]
#include <unistd.h>

void      ft_putchar(char c)
{
      write(1, &c, 1);
}

void    ft_putnbr(int nbr)
{
    write(1, &nbr, 1);
}

void      ft_ft(int *nbr)
{
      *nbr = 42;
}

int      main(void)
{
      int a;
      int *ptr;
      char c;

      a = 7;
      ptr = &a;
      ft_ft(ptr);
    ft_putnbr(a);
      ft_putchar('\n');
}
/code]