The HP-65 was the first programmable handheld calculator in the world. Introduced by Hewlett-Packard in 1974, it was considered an electronic marvel. It packed 9 storage registers and had room for 100 keystroke instructions. It also included a magnetic card reader/writer whose cards were approximately the size of a chewing gum stick.

The HP-65 offered very rudimentary program editing capabilities, however, and its storage register R9 was corrupted whenever the user (or program) executed trigonometric functions or performed comparison tests. This problem was documented in the manual, so it's not considered a bug.