BleepingComputer.com: Pointer Arithmetic

#include <iostream>
#include <ctype.h>
#include <string.h>

using namespace std;

bool GetWord(char* theString, char * word, int& wordOffset);

int main() {
	const int bufferSize = 255;
	char buffer[bufferSize+1]; //hold the entire string
	char word[bufferSize+1];   //hold the word
	int wordOffset = 0;		//start at the beginning

	cout << "Enter a string: ";
	cin.getline(buffer,bufferSize);

	while (GetWord(buffer, word, wordOffset))
	{
		cout << "Got this word: " << word << endl;
	}
	return 0;
}

//function to parse words from a string
bool GetWord(char* theString, char* word, int& wordOffset)
{
	if (theString[wordOffset] == 0) //end of string
		return false;

	char *p1, *p2;
	p1 = p2 = theString + wordOffset; //Point to the next word

	//eat leading space
	for (int i = 0; i < (int)strlen(p1) && !isalnum(p1[0]); i++)
		p1++;

	//see if you have a word
	if(!isalnum(p1[0]))
		return false;

	//p1 now points to start of next word
	//p2 needs to point there to
	p2 = p1;

	//march p2 to end of the word
	while(!isalnum(p2[0]))
		p2++;

	//p1 at beginning
	//p2 at the end
	//length of word is the difference
	int len = int (p2 - p1);

	//copy word into the buffer
	strncpy (word,p1,len);

	//null terminate at
	word[len]='\0';

	//now find the beginning of the next word
	for (int j = int(p2-theString); j<(int)strlen(theString)
		&& !isalnum(p2[0]); j++)
	{
		p2++;
	}

	wordOffset = int(p2-theString);

	return true;
}

#include <iostream>
#include <locale>
int main(){
locale loc("German_Germany");
cout << isalnum('_',loc);
return 0;
}

while(!isalnum(p2[0]))	 p2++;