MacWrite

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.

Programming libraries

 * libmwaw: reads old MacWrite and ClarisWorks documents

Sample files

 * https://telparia.com/fileFormatSamples/document/macWrite/

Links

 * Wikipedia article
 * MacWrite 2.2 format description
 * Discussion of converting old MacWrite documents
 * Another discussion
 * In Search of MacWrite - Changing Type/Creator to open