Similar in appearance to the IBM 5100 from five years earlier in 1975, the Hewlett-Packard HP-85 is an all-in-one portable computer system with a built-in keyboard, 5" screen, thermal printer, tape storage unit, and the BASIC programming language.
Why does HP use its own custom CPU? One of the most important reasons is ACCURACY. Where other computers do binary arithmetic, the HP-85 does its arithmetic in BCD (binary coded decimal). HP calculators do BCD arithmetic, and they spent years testing and perfecting those algorithms, so you can trust that the answers returned by the HP-85 are accurate to 12 digits. Real number calculations in the hp-85 are performed internally to 15 significant decimal digits and rounded to 12 digits for presentation.