The original ''dc'' interpreter appeared in Version 1 (V1) AT&T UNIX. Therefore, ''dc'' precedes the C language (appeared in V3 UNIX) and the Bourne Shell (appeared in V7 UNIX). The authors programmed the interpreter in PDP-11 Assembly, and later rewrote it in C language. AT&T dc became the back end of AT&T bc in V6 UNIX. AT&T dc survives in systems that descend from System V, including Solaris.
POSIX only describes ''bc'', not ''dc''; so AT&T dc is the only reference. Other implementations (like GNU dc and OpenBSD dc) follow AT&T dc by implementing the same commands.
The manual page accidentally omits !< != !>, but AT&T dc does have these commands, and ''dc'' programmers do use them.
Ancient dc
[http://www.tuhs.org/wiki/The_Unix_Heritage_Society The Unix Heritage Society] preserves old versions of AT&T UNIX.
- [http://minnie.tuhs.org/cgi-bin/utree.pl?file=V1/man/man1/dc.1 dc(I) manual], Version 1 AT&T UNIX
- [http://minnie.tuhs.org/cgi-bin/utree.pl?file=V2/cmd source code] (dc1.s to dc5.s), Version 2 AT&T UNIX
Modern dc
The [http://heirloom.sourceforge.net/ Heirloom Project] provides AT&T dc along with other System V commands.
- [http://heirloom.sourceforge.net/man/dc.1.html dc(1) manual] and [http://heirloom.cvs.sourceforge.net/viewvc/heirloom/heirloom/dc/ source code]