By default, the picture character Z always allows entry of any character code from 0 to 255. This includes allowing the entry of keycodes for non-printable characters.
In contrast, the picture control characters A, X, *, and ! allow entry only of characters in the keycode range of 32 through 127. This does not allow the user to enter the international characters and symbols that are available in the IBM Extended Character Set and various other character sets available for other terminals and operating systems.
The IBM Extended Character Set extends the normal ASCII character set by including symbols, international letters, Greek letters, line drawing characters, and block graphics characters. The Extended Character Set has keycodes ranging from 0 to 255 and is recognized by the IBM PC, PS/2, and most compatible clones.
You can enable support for characters in the range of 128 to 255 by including the extended character set header file vv_extch.h.
When vv_extch.h is #included, A, X, *, and ! will recognize characters in the Extended Character Set. "A" recognizes all the alphabetic characters, "X" recognizes all printable characters except block graphics and line drawing characters, and "!" and "*" correctly convert international characters to uppercase and lowercase, respectively.
Terminal-Based Users: If you are using a system that has a different character set than that used by the IBM PC, you will want to review the table used by the system to convert lowercase alphabetic characters to uppercase. There may be discrepancies in the mappings. See Chapter 49, "Utility Functions," for more information.
