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.
The manual page accidentally omits
!< != !>, but AT&T dc does have these commands, and dc programmers do use them.
The Unix Heritage Society preserves old versions of AT&T UNIX.
The Heirloom Project provides AT&T dc along with other System V commands.