Introduction and RPN calculator advice

[floppy]

My recommendation (apart from the nice links or overviews given in this thread): whatever you choose for your needs,
- when you like a calculator, buy 3 of them for avoiding running after them in few years
- buy only a calculator with possibility of external storage; ideally in a PC/ARM so you can print from there for documentation purpose (= plan B in case the batteries are dead or another person need the program)