If it doesn't have an Enter key, it's not RPN

[Didier Lachieze]

(02-07-2015 04:42 PM)Den Belillo (Martinez Ca.) Wrote:  It showed up a lot in the early days of calculators when companies bought a TI chip and built their own calcs around it. They often used that same += & -=, probably to save one key. The Privileg Beginner / Harvard 606, the supercal 616, and the Commodore 6 & 6x all had keys printed +=, -=, x= and /=. All were two level stack RPN, or postfix Only the 6 lacked an enter key but all could be used without ever pressing enter.

Not only in the early days: