C语言实现字符串到数值的转换

#include <stdio.h>

int main() { char str[100];

printf('Enter a string:');
scanf('%s', str);

int num = 0;
int i = 0;

while (str[i] != '\0') {
    num = num * 10 + (str[i] - '0');
    i++;
}

printf('digit=%d', num);

return 0;

}