Register Arithmetic on the 12c

On Friday I forgot my HP15c LE at work. I hope to find it back on Monday morning.

So I had to make do with an HP12c anniversary when I went out for shopping, trying to keep count of the money spend on purchases. As I had been using a program before, and I wanted to keep the data used, I did not want to use the first 4 registers.

So I entered 99 € STO 5 (first purchase) and 29,95 STO + 5 and bang! Error 4 appears on screen! I try with other register: STO+6: Error 4!!

Neither recall arithmetic was working with any register

I was desperate! was my program using too many registers? No: 17 registers left.

Was there a bug in the system? I had to wait until yeterday night to try with another original HP12c (US made 1985): it did not work either. Well: at least I dod not have a defective sample.

I had then to go to the manual and check about register arithmetic. Gosh! I found there that a) register arithmetic just work with registers up to 4; and b) there is not recall arithmetic.

While the 12c is a very stylish calculator, and is very appropriated for every day business work (the three percentage keys are very much used in any kind of analysis, and very well placed), it has several points that make prefer the HP15c for every day work (and the 17bII+ for pure, desktop business work)

• There's no backspace key. If you entered something wrong, you are out of luck - you need to clear the whole screen.
• Register arithmetic is not consistent: it does not have recall arithmetic, and no sto arithmetic for registers 5 and up
• It lacks base 10 logs and exponential (you can always make do with other mathematical approach).