The ++ operator appears to have been.
One would expect that most people on this list would have read "The
Development of the C Language", by Dennis Ritchie, which makes perfectly clear
(at 'More History') that the PDP-11 had nothing to do with it:
Thompson went a step further by inventing the ++ and -- operators, which
increment or decrement; their prefix or postfix position determines whether
the alteration occurs before or after noting the value of the operand. They
were not in the earliest versions of B, but appeared along the way. People
often guess that they were created to use the auto-increment and
auto-decrement address modes provided by the DEC PDP-11 on which C and Unix
first became popular. This is historically impossible, since there was no
PDP-11 when B was developed.
https://www.bell-labs.com/usr/dmr/www/chist.html
thereby alleviating the need for Ken to chime in (although they do allow a
very efficient implementation of it).
Too much to hope for, I guess.
Noel