It is likely that the FX-501P/502P were the first LCD programmable calculators to be produced as up until 1979 (and the introduction of the HP-41C) no manufacturer had introduced such a device.

The display was covered with a yellow filter, supposedly to prevent ultra-violet radiation damage to the unstable (at the time) Liquid Crystal compound.

The FX-501P and FX-502P supported indirect addressing both for memory access and jumps and therefore the programming model could be considered Turing complete.

Since the FX-501P and FX-502P only employed a seven-segment display each program step was represented by a special 2-digit codes made up of the digits 0 .. 9 and the character C, E, F and P. The calculator came with a special overlay[2] so the user did not need to memorize the mapping between code and actual command.

What differentiated the FX-501 / FX-502P from its competitors was that programming was retained in a battery-buffered memory when the calculator was turned off.