Why did the number 4 after adding the symbol “0” become the symbol “4”?

October 21, 2023

I wrote a program that prints the same number that was passed as an argument. The code works, but I don’t understand the process of converting numbers to characters. How does this work at the machine level? Why, when I add the zero symbol, do I get the four symbol from the number 4?

#include <stdio.h>

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

void    ft_putnbr(int nb)
{
    if (nb >= 10)
    {
        ft_putnbr(nb / 10);
        ft_putnbr(nb % 10);
    }
    else
    {
        ft_putchar(nb + '0');
    }
}

int main()
{
    ft_putnbr(42);
    return 0;
}

I don’t understand the process of converting a number into a symbol in this case.

>Solution :

'0' is just the human readable represetation of the integer 48 which is considered as code for the character '0' in ASCII.

ASCII digit codes:

decimal	octal	hex	binary	character
48	060	30	0110000	0
49	061	31	0110001	1
50	062	32	0110010	2
51	063	33	0110011	3
52	064	34	0110100	4
53	065	35	0110101	5
54	066	36	0110110	6
55	067	37	0110111	7
56	070	38	0111000	8
57	071	39	0111001	9