Why doesn't the loop exit?

Question

I have my program prompting the user for a code in letters.
System.out.print("Enter Code: ");
code = TextIO.getlnString();
code = code.toUpperCase();
//uppercase so I don't have to code for small letters tooFollowing this I'm using a while loop to check if the code contains numbers or anything other than letters.
hecknum = (int) code.charAt(p);
while ((checknum >= 91) || (checknum <= 64)) {
System.out.println();
System.out.println("Codes may only contains letters from A to Z.\n");
System.out.print("Enter Code: ");
code = TextIO.getlnString();
code = code.toUpperCase();
}This only works partially however. If I enter letters the first time through, everything will work fine.
If I enter numbers or some other symbols, I get the error and am re-prompted for the code. Thing is, if I enter only letters the second time around, I get the error message again, as if I had entered numbers or something.
I have no clue why... from what I see it should work...
Can anyone help me figure this out?

Answer 1

inside the while loop you never change the value of checknum, so if the codition is tru when you enter the loop, it stays true
looks like you need to change p and recalculate checknum