HP-75D

The HP-75C and HP-75D were hand-held computers programmable in BASIC, made by Hewlett-Packard from 1982 to 1986. The HP-75 had a single-line liquid crystal display, 48 KiB system ROM and 16 KiB RAM, a comparatively large keyboard (albeit without separate numeric pad), a manually operated magnetic card reader (2×650 bytes per card), 4 ports for memory expansion (1 for RAM and 3 for ROM modules), and an HP-IL interface that could be used to connect printers, storage and electronic test equipment. The BASIC interpreter also acted as a primitive operating system, providing file handling capabilities for program storage using RAM, cards, or cassettes/diskettes (via HP-IL).