 the hp-41c series are programmable, expandable, continuous memory handheld rpn calculators made by hewlett-packard from 1979 to 1990. the original model, hp-41c, was the first of its kind to offer alphanumeric display capabilities. later came the hp-41cv and hp-41cx, offering more memory and functionality. ==the alphanumeric "revolution"== the alphanumeric lcd screen of the hp-41c revolutionized the way a calculator could be used, providing user friendliness (for its time) and expandability (keyboard-unassigned functions could be spelled out alphabetically). by using an alphanumeric display, the calculator could tell the user what was going on: it could display meaningful error messages ("zero divide") instead of simply a blinking zero; it could also specifically prompt the user for arguments ("enter radius") instead of just displaying a question mark. earlier calculators needed a key, or key combination, for every available function. the hp-67 had three shift keys; the competing texas instruments calculators had two (2nd and inv) and close to 50 keys (the ti-59 had 45). hewlett-packard were constrained by their one byte only instruction format. the more flexible storage format for programs in the ti-59 allowed combining more keys into one instruction. the longest instruction required eleven keypresses, re-using the shift keys four times. the ti-59 also made use of the op key, followed by two digits, to access another 40 different functions. but the user had to remember the codes for them. clearly, a more convenient and flexible method of executing the calculator's instructions was urgently needed. the hp-41c had a relatively small keyboard, and only one shift key, but provided hundreds of functions. every function that was not assigned to a key could be invoked through the xeq key (pronounced exeqte &mdash; "execute") and spelled ou
1979_introductions HP_calculators Programmable_calculators