Character Counter

#include <iostream>

using namespace std;

int main(int argc, char const *argv[])
{
    int ch;
    unsigned counter[256] = {0};

    while ((ch = cin.get()) > 0)
    {
        counter[ch]++;
    }

    unsigned count_alpha = 0;
    unsigned count_digit = 0;
    unsigned count_space = 0;
    unsigned count_other = 0;

    for (int i = 0; i < 256; i++)
    {
        if (isalpha(i))
        {
            count_alpha += counter[i];
        }
        else if (isdigit(i))
        {
            count_digit += counter[i];
        }
        else if (isspace(i))
        {
            count_space += counter[i];
        }
        else
        {
            count_space += counter[i];
        }
    }

    cout << "count_alpha = " << count_alpha << endl;
    cout << "count_digit = " << count_digit << endl;
    cout << "count_space = " << count_space << endl;
    cout << "count_other = " << count_other << endl;

    return 0;
}