updated for version 7.0066
diff --git a/runtime/doc/develop.txt b/runtime/doc/develop.txt
index 6e4f4e3..bc8b0e8 100644
--- a/runtime/doc/develop.txt
+++ b/runtime/doc/develop.txt
@@ -1,4 +1,4 @@
-*develop.txt* For Vim version 7.0aa. Last change: 2004 Jan 17
+*develop.txt* For Vim version 7.0aa. Last change: 2005 Mar 29
VIM REFERENCE MANUAL by Bram Moolenaar
@@ -366,7 +366,33 @@
fit in the shell.
-To be continued...
+Spell checking *develop-spell*
+
+When spell checking was going to be added to Vim a survey was done over the
+available spell checking libraries and programs. Unfortunately, the result
+was that none of them provided sufficient capabilities to be used as the spell
+checking engine in Vim, for various reasons:
+
+- Missing support for multi-byte encodings. At least UTF-8 must be supported,
+ so that more than one language can be used in the same file.
+- For the programs and libraries: Using them as-is would require installing
+ them separately from Vim. That's not impossible, but a drawback.
+- Performance: A few tests showed that it's possible to check spelling on the
+ fly (while redrawing), just like syntax highlighting. But the mechanisms
+ used by other code are much slower. Myspell uses a simplistic hashtable,
+ for example.
+- For a program like aspell a communication mechanism would have to be setup.
+ That's complicated to do in a portable way (Unix-only would be relatively
+ simple, but that's not good enough). And performance will become a problem
+ (lots of process switching involved).
+- Missing support for words with non-word characters, such as "Etten-Leur" and
+ "et al.", would require marking the pieces of them OK, lowering the
+ reliability.
+- Missing support for regions or dialects. Makes it difficult to accept
+ all English words and highlight non-Canadian words differently.
+- Missing support for rare words. Many words are correct but hardly ever used
+ and could be a misspelled often-used word.
+
==============================================================================
4. Assumptions *design-assumptions*