Differences between Release 2 and Release 3

Gray runs now on Tile Release 2.1. It uses Tile's new "source" and
"line" words for displaying error locations. Therefore it does not
work on Release 1 of Tile.
Some portability bugs have been removed.

Differences between Release 1 and Release 2

Gray now runs on computers with memory alignment restrictions, too.
Tile Release 2 is now supported, it needs porting to run on Tile
Release 1.
Changed "(compile)" into "compile," (ANSI).
No bugs were reported. Therefore they are still there.
