How do I fix the endless production of my code?

The code is a four-character password generator. I have an if/else break system setup, but I can't figure out why it isn't working. The loop generates past the limit until it exhausts all options, which I'm having a hard time properly debugging. I'm very new to anything other than javascript and HTML, so any help would be useful. Thanks!

#include <iostream>
using namespace std;

int
main ()  {
  char char1;
  char char2;
  char char3;
  char char4;
  int numPasswordsGenerated = 0;

  cout << "Password Generator:" << endl;

  /* Generates four-character passwords (excludin digits) by exhausting all character
     options between '!' and '~' starting with the fourth character. Once the fourth 
     character exhausts all options, the third character increases by the next character 
     in the binary lineup, then continuing with the fourth character. This process continues 
     until the numPasswordsGenerated integer reaches the desired number, or the password 
     output becomes "~~~~"; whichever comes first.
   */
  char1 = '!';
  while (char1 <= '~')    {
      char2 = '!';
      while (char2 <= '~')    {
          char3 = '!';
          while (char3 <= '~')    {
              char4 = '!';
              while (char4 <= '~') {
                  // cout << char1 << char2 << char3 << char4 << endl;
                  numPasswordsGenerated++;                  //!*FIXME*!
                  cout << numPasswordsGenerated << endl;    //DEBUG DELETE
                  if (numPasswordsGenerated == 10)
                    break;
                    
                  char4++;
                  
              }
          char3++;
              
          }
      char2++;
          
      }
      char1++;
      
  }

  return 0;
}