From: utzoo!henry
Newsgroups: hacknews
Title: dc, bc fixed 
Article-I.D.: utzoo.2803
Posted: Mon Feb  7 20:00:55 1983
Received: Mon Feb  7 20:00:55 1983

Dc(1) has been fixed so that if its input is a tty and the -q option
is not specified, it prints a message telling how to exit from it.
This is a bit of a blemish, but "dc" is too damned close to "cd" for
comfort, and confusion has been observed several times.  At the same
time I cleaned up dc's option handling slightly, and therefore had to
fix up bc(1) not to invoke dc using an obsolete option.