Restrictions on Pictures for Full Editing

You must observe certain restrictions on the picture if you want your user to be able to insert, delete, and backspace over characters in the field.

In order to use these capabilities, the field picture must be "pure," consisting of picture control characters that allow the same type of character entries. This means that the picture:

• nCannot contain mixtures of alphabetic (X, A, Z, *, !) and numeric picture control characters (U, 9, #, @).
  
  
• nCannot contain mixtures of Xs, As, and Zs. The picture control characters ! and *, which convert letters to uppercase or lowercase, do not destroy the purity of either a string of Xs, Zs, or As.
  
  
• nCannot contain mixtures of Us, 9s, and #s.

As the user types characters into the field, each character is validated against the picture control character in that particular location. If the picture is not pure, the user is not allowed to delete or insert characters, or to use the destructive backspace that shifts other characters to the left. This restriction is necessary to avoid shifting characters into new positions where they might not be valid.