HP-75C and HP-75D
The Hewlett-Packard HP-75 series of portable handheld computers were a miniaturized version of the HP-85 computer architecture. The HP-75 had a single-line 32-character LCD, 16kB of RAM (plus an optional HP 82700A 8kB expansion pack for 24kB total), 48kB of ROM, three slots for add-on ROM modules, an HP-IL interface, and a manually-operated magnetic card reader and writer (1300 bytes per card). The HP-75D model added an additional port for a barcode reader wand.
The HP-75 runs BASIC and has additional functionality, such as a time and date display, text editor, ability to set appointment reminders (with alarms), etc.
HP also made an expansion pod for the HP-75 — the HP 82718A. This pod contains a built-in 64kB (Opt 064) or 32kB (Opt 032) electronic disc for storing files, and a 300-baud modem. It also adds BASIC commands for scanning Code 11 and Code 39 barcodes.
The HP-IL ports on the computer can be used to connect to various devices, such as:
- HP 82161A Digital Cassette Drive
- HP 82162A Thermal Printer
- HP 82163A Video Interface
- HP 82164A RS232 Interface
- HP 82169A HP-IB Interface
- HP 9114 floppy drive
- various HP instruments with HP-IL connectivity (multimeters, logic analyzers, etc.)
I have two HP-75 computers — a HP-75C and a HP-75D. Both have the 82700A 8kB RAM expansion pack for a total of 24kB of RAM. The HP-75C has the I/O, Math, and VisiCalc ROM modules. The HP-75D is connected to the 82718A expansion pod.
- HP-75 Owner's Manual (PDF, 4.3MB)
- HP-75 Reference Manual (PDF, 780kB)
- HP-75 Service Manual (PDF, 6.2MB)
- HP Journal (June 1983) (PDF, 9.6MB) — contains interesting articles about the HP-75 and its card reader.
- HP-75 I/O ROM Programming Techniques Manual (PDF, 1.2MB) — shows you how to use commands from the I/O ROM to control devices over HP-IL.
- HP 82718A Expansion Pod Reference Manual (PDF, 10MB)
- HP-75 Handheld Computers Group — a mailing list with lots of interesting information about the HP-75 computers.