(12C) Does a STO pop the stack or not?

[Joe_H]

HP-12C (3rd generation model, I gather, no. HSTNJ-KN05 made in China with 2xCR2032 and a serial port) purchased around 2010:

- On the 12C I have confirmed that a STO {0-9} doesn't pop the stack and the 0 is pushed onto it.
- However, for STO {n, i, PV, PMT & FV} it does pop the stack when a digit is entered after the STO line.
- If the stack is rotated immediately after the STO the digit entered into the TVM register remains on the stack.
- If the STO is followed by a RCL # or LSTx the value stored is popped off the stack and replaced with the register value or LSTx.


HP-12C Platinum (HSTNJ-KN11 2xCR2032 model made in Philippines no serial port installed but chassis shaped for the plug) purchased 2019:

- On the Platinum it is the same for STO {0-9} as STO {n, i, PV, PMT & FV} in that the valued stored in the TVM register is not popped if followed by another value either by direct entry of RCL or LSTx.

The behaviour of the Platinum is more consistent and easier to understand but the incompatibility is a real pain.

What did the original HP-12C from 1981 do?