PETSCII also has a "text mode", in which lowercase letters occupy the range $41–$5A, and uppercase letters occupy the range $C1–$DA. The mode is toggled by holding one of the SHIFT keys and then pressing and releasing the "Commodore" key. Regardless of whether the chip has undergone this graphic "shift", there are block graphic characters in the range of $E0-FF. This serves to distinguish PETSCII from those kinds of ASCII that go back no farther than ASCII-1967, so any text transfer between an 8-bit Commodore machine and one that uses 1967-derived ASCII would result in text where uppercase letters appear to be lowercase, and lowercase letters uppercase. There is no easy Boolean operation to change these cases to the proper case. Thus, as with other computers based on non-standard-ASCII character sets, software conversion is needed when exchanging text files and/or telecommunicating with standard ASCII systems. The other ranges are unchanged in shifted mode; this means that the other characters added in ASCII-1967 besides lowercase lettersi.e. the grave accent, curly braces, vertical bar, and tildedo not exist in PETSCII.