UTF-EBCDIC
| Created by | IBM |
|---|---|
| Definitions | Unicode Technical Report #16 |
| Based on | UTF-8 |
| Transforms / Encodes | Unicode |
UTF-EBCDIC is a character encoding capable of encoding all 1,112,064 valid character code points in Unicode using 1 to 5 bytes (in contrast to a maximum of 4 for UTF-8).[1] It is meant to be EBCDIC-friendly, so that legacy EBCDIC applications on mainframes may process the characters without much difficulty. Its advantages for existing EBCDIC-based systems are similar to UTF-8's advantages for existing ASCII-based systems. Details on UTF-EBCDIC are defined in Unicode Technical Report #16.
To produce the UTF-EBCDIC encoded version of a series of Unicode code points, an encoding based on UTF-8 (known in the specification as UTF-8-Mod) is applied first (creating what the specification calls an I8 sequence). The main difference between this encoding and UTF-8 is that it allows Unicode code points U+0080 through U+009F (the C1 control codes) to be represented as a single byte and therefore later mapped to corresponding EBCDIC control codes. In order to achieve this, UTF-8-Mod uses 101xxxxx instead of 10xxxxxx as the format for trailing bytes in a multi-byte sequence. As this can only hold 5 bits rather than 6, the UTF-8-Mod encoding of codepoints above U+03FF are larger than the UTF-8 encoding.
The UTF-8-Mod transformation leaves the data in an ASCII-based format (for example, U+0041 "A" is still encoded as 0x41), so each byte is fed through a reversible (one-to-one) lookup table to produce the final UTF-EBCDIC encoding. For example, 0x41 in this table maps to 0xC1; thus the UTF-EBCDIC encoding of U+0041 (Unicode's "A") is 0xC1 (EBCDIC's "A").
UTF-EBCDIC is rarely used, even on the EBCDIC-based mainframes for which it was designed. IBM EBCDIC-based mainframe operating systems, such as z/OS, usually use UTF-16 for complete Unicode support. For example, IBM Db2, COBOL, PL/I, Java and the IBM XML toolkit support UTF-16 on IBM mainframes.
Codepage layout
[edit ]There are 160 characters with single-byte encodings in UTF-EBCDIC (compared to 128 in UTF-8). As can be seen, the single-byte portion is similar to IBM-1047 instead of IBM-37 due to the location of the square brackets. CCSID 37 has [] at hex BA and BB instead of at hex AD and BD respectively.
UTF-EBCDICOracle UTFE
[edit ]Oracle UTFE is a Unicode 3.0 UTF-8 Oracle database variation, similar to the CESU-8 variant of UTF-8, where supplementary characters are encoded as two 4-byte characters rather than a single 4- or 5-byte character. It is used only on EBCDIC platforms.[2]
See also
[edit ]References
[edit ]- ^ "UTR #16: UTF-EBCDIC". www.unicode.org. Retrieved 2021年02月23日.
You need to search at most five bytes (seven bytes, if the full range of 31 bits of ISO/IEC 10646 is considered) backwards
- ^ Baird, Cathy; Chiba, Dan; Chu, Winson; Fan, Jessica; Ho, Claire; Law, Simon; Lee, Geoff; Linsley, Peter; Matsuda, Keni; Oscroft, Tamzin; Takeda, Shige; Tanaka, Linus; Tozawa, Makoto; Trute, Barry; Tsujimoto, Mayumi; Wu, Ying; Yau, Michael; Yu, Tim; Wang, Chao; Wong, Simon; Zhang, Weiran; Zheng, Lei; Zhu, Yan; Moore, Valarie (2002) [1996]. "Appendix A: Locale Data". Oracle9i Database Globalization Support Guide (PDF) (Release 2 (9.2) ed.). Oracle Corporation. Oracle A96529-01. Archived (PDF) from the original on 2017年02月14日. Retrieved 2017年02月14日.
External links
[edit ]- V.S. Umamaheswaran, Unicode Technical Report #16: the definition of UTF-EBCDIC (2002年04月16日)