Suppressing the Use of Selected Control Characters

Applications may sometimes want to suppress the use of certain control characters. For instance, an application which stores lines of text within a group may want to suppress the division of each group expression into separate elements, so that the whole group expression is stored as a single name within the group. One way to do this would be to set the DELIMITER control character to a character which is guaranteed not to occur within the supplied text. However, such a character may not exist. A more flexible approach is to assign the value of the NULL control character to the DELIMITER control character. For instance, if the NULL and DELIMITER characters are both set to ``%'', then the group expression is not split up into elements delimited by ``%'' signs. Note, any ``%'' signs in the group expression will be included in the name stored in the group without any change. The NULL character can be assigned to any of the other control characters to suppress the use of those control character. The only restriction is that if one of the two control characters OPEN_NEST and CLOSE_NEST is assigned the NULL value, then the other one must also be assigned the NULL value. The same restriction applies to the OPEN_KERNEL and CLOSE_KERNEL control characters.