Creating an atoi function

Question

I\'m attempting to create my own atoi function. With the following I\'m getting a return value of 0. Whatever I change the number variable within the function is what I get

Answer 1

1. You're declaring an array of char *, that is, an array of strings, rather than a single string. You probably want:

   char number[MAXSIZE];
   

2. Your scanf format string is wrong. If you want to read a string, you should use %s. %c reads only a single character.

3. Your scanf parameter is wrong - pass number itself (or &number[0] if you prefer), not &number.

4. The parameter you're passing to atoi_me is wrong. Call it with number (or equivalently &number[0]), not *number.

Putting all of that together, you should have a main routine something like this:

int main(void)
{
    char number[MAXSIZE];
    int num;
    printf("Please enter a number: ");
    scanf("%s", number);
    num = atoi_me(number);
    printf("%d\n", num);
    return 0;
} 

Editorial notes: You have a potential buffer overflow with the scanf line. You'd be better off using a function like fgets(3) that makes it easy to protect against that kind of problem.

atoi(3) also traditionally supports negative numbers (with a leading -) and an optional leading + for positive numbers, which your implementation doesn't handle.