charater testing for password verification

just wanted to know if someone could point me in the right direction on a problem I'm trying to solve.
here it is:
Need to bulid software that reqires user password to meet following criteria.
1.Password should be atleast 6 chars long
2.Password should contain at least one uppercase and one lowercase letter
3.The password should contain one digit,

Now can the whole string be tested using a for loop and if-statements or does each character need to be tested induvidually.

#1. Use the strlen() function in string.h to check lengths of strings for comparisons.

#2. Use the isupper() and islower() in ctype.h (or cctype for ANSI) to find if characters are uppercase or lower case.

#3. Use the isdigit() in ctype.h (or cctype for ANSI) to find if a character is a digit.

You will have to parse the password string character by character like this:

Code:

---

while( *string != '\0')
{
  if( isupper(*string) )
      // Do whatever
  if( isdigit(*string) )
      // Do whatever
 
  string++  // Point to next character
}

---

Good luck...