slackbuilds/development/dasm/vcs-old.txt

Around 2003, the Atari 2600 vcs.h file changed greatly, in ways that
make it somewhat incompatible with the older vcs.h. For instance,
Thomas Jentzsch's River Raid commented source no longer assembles
correctly with the new vcs.h.

If you need it, there's a copy of the old vcs.h from around 2000 included
in the dasm package as: /usr/share/dasm/machines/atari2600/vcs.h.old

New projects should use the new vcs.h; the old one exists only for
backwards compatibility with old sources.