HP-71B SUPERLEX LEX File Manual

[rprosperi]

In the HP world, the HP-75C/D and the HP-83/85/86/87 series all used similar processes to extend their BASIC vocabulary. (The same may be true for the 9x00 series desktop computers, I'm not sure how they worked.) The 75 series used RAM (or ROM) based LEX files, similar to the 71B, while the Series-80 used ROM-based extensions (e.g. Graphics ROM added new commands for Graphics features, etc.). The 71 and 75 series LEX files could be copied into the machine's RAM, while for Series-80, the ROM module must be present.

As for the 71B itself, there were many (at least 10?) companies developing/selling LEX files for various kinds of applications, utilities, etc.