C program to convert string of numbers to their numeric equivalent

atoi program in C

#include <stdio.h>

int main()
{
    int atoi (char s[]);
    
    printf("%d",atoi("239"));
    return 0;

}

int atoi(char s[])
{
    int i,n;
    
    n = 0;
    
    for(i=0;s[i]>= '0' && s[i] <= '9'; ++i)
        n = 10 * n + (s[i] - '0');
    return n;
}