The HP-28C/S programmable pocket calculator shown above was the first machine offering RPL (Reverse Polish LISP) as its programming language - it by far outperformed its predecessors like the HP 67 or the HP 41C/CV/CX in terms of sheer speed as well as in programming capabilities. With 32 kB of RAM (HP 28S, the HP 28C only had 2 kB of RAM) it is a programmers dream and way more than just another programmable pocket calculator.