how to use isdigit(ch)

[flyraf821]

I need to count the number of digits in a series of strings. I have found the isdigit(ch) function in the cctype header but I am not sure of how to use it. I googled it and did not find any useful information that would help me understand it. If I understand it correctly it returns true if digit between 0-9 and false otherwise. I guess the problem I am having is applying this by checking each character in a string and counting.

void count_digit(string& word)
{
   int wlength;
   char ch;
   wlength = word.length();
   for (int i=1; i<wlength; i++)
    {
}

thats all i have come up with i'm not sure how to go through each character and then sum up the digits. I guess I can use a runnig counter but the true/false is throwing me off. any assistance would be greatly appreciated.

[jsmith]

word[i] accesses the ith character of the string.
isdigit( ch ) returns non-zero if the character is a digit or zero otherwise.