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File Format
Name MacWrite
Type Code MW2D
Wikidata ID Q1430257
Released 1984

MacWrite was the word processor on early Macintosh computers. It originally was released by Apple as one of the programs that came with a Macintosh, but was later spun off to Claris as a separate software product; this did not succeed in competition with other word processors, so it was eventually discontinued by the mid-1990s.


File identification

The first two bytes of a MacWrite file are a big-endian integer distinguishing MacWrite versions.

MacWrite versions 1.0 - 2.2 used version 00 03 in this field.

MacWrite versions 4.5 - 5.0 used version 00 06 in this field.

MacWrite II used version 00 2E in this field.

MacWrite Pro used version 00 04 in this field.

Format details

MacWrite 2.2 stored text in a compression scheme where the (language-specific) most common characters (for English, " etnroaisdlhcfp" in that order, with the space character first) were stored as one nybble each (half a byte), where the values 0 through E corresponded to the characters in the most-common list. The nybble value F signaled that a different character followed, meaning that characters not on the list took three nybbles (a byte and a half) to store. This usually averaged out to a savings, since the most common characters typically make up a high portion of the text.

MacWrite 3.x and up used a different compression system, and were designed so files could be edited directly on disk without loading the entire file into memory.

Version History

Version 1.0 1984.01.24 Encore Systems WORD/MACA
Version 2.2 1984.05 Encore Systems WORD/MACA
Version 4.5 1985.04 Encore Systems WORD/MACA
Version 4.6 1987.07 Encore Systems WORD/MACA
Version 5.0 1988.03 Claris WORD/MACA
Version II 1989.01 Claris MW2D/MWII
Pro 1.0 1993.03 Claris MWPd/MWPR
Pro 1.5 1994 Claris MWPd/MWPR

Programming libraries



Sample files


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