ISO/IEC JTC1/SC2/WG2  N 2277






 Coded Character Set

Secretariat: Japan (JISC)




Doc. Type:    Proposed amendment to part 1 of ISO/IEC 10646


Title:           Addition of reserved characters for internal processing uses


Source:        USA (NCITS/L2)

Project:        JTC1 02.18

Status:          For review by WG2

Date:            2000-09-19

Distribution: WG2





Implementation experience since first adopting 10646:1993 has shown that there is a need for an additional number of BMP character positions that can be used internally to an implementation and are guaranteed not to be characters for interchange in the same manner as U+FFFF, therefore L2 requests the following modifications to ISO/IEC 10646-1:


Clause 7. Remove the Note (because the note really only applies to characters from the BMP it should be located in clause 8).


Clause 8. Replace the last paragraph as follows:


Code positions 0000 FDD0 to 0000 FDEF, 0000 FFFE and 0000 FFFF are reserved.


NOTE – Code position 0000 FFFE is reserved for “signature” (see annex H). Code positions 0000 FDD0 to 0000 FDEF and 0000 FFFF can be used for internal processing uses requiring numeric values that are guaranteed not to be coded characters, such as in terminating tables, or signaling end-of-text. Furthermore, since 0000 FFFF is the largest BMP value, it may also be used as the final value in binary or sequential searching index within the context of the BMP.