This is GNU dc.  (Taken from the GNU bc 1.03 distribution.)

ALL other files distributed with GNU dc are available in some form in
/usr/src/gnu/usr.bin/bc.  (aka ../bc)

The files array.c, eval.c, misc.c, stack.c and string.c were renamed from
their original distribution names as dc-xxxx.c.

An original distribution of GNU bc/dc can be regenerated from the files
in the directories bc and dc.  (It will require GNU autoconf 2.0 to 
regenerate some files.)