Count spaces, uppercase and lowercase in a sentence using C

#include
int main() {
   char str[100],i;
   int upper = 0, lower = 0, number = 0, special = 0,whitesp=0;
   printf("enter string");
   gets(str);
   for (i = 0; i < str[i]!='\0'; i++) {
      if (str[i] >= 'A' && str[i] <= 'Z')
         upper++;
      else if (str[i] >= 'a' && str[i] <= 'z')
         lower++;
      else if (str[i]>= '0' && str[i]<= '9')
         number++;
      else if(str[i]==' ')
         whitesp++;
      else
         special++;
   }
   printf("Upper case letters: %d
",upper);
   printf("lower case letters: %d
",lower);
   printf("Numbers: %d
",number);
   printf("whitespace: %d
",whitesp);
   printf("sp chararcter: %d
",special);
   return 0;
}