The HP-75C was the first pocket computer ever produced by HP who wanted a pocket book format (10”x 5”) computer as powerful as a desktop. It can also be considered as the first organizer able to deal with a multiple alarms time schedule, to control real time peripherals and to memorize text files.
Its 48KB ROM contained a very complete Basic language and a light version of the spreadsheet Visicalc. Three slots allowed adding pre-programmed ROM modules (Maths, finance, word processor…)
It integrated a card reader. The cards was manually slipped front of the magnetic head. Each card could stock 1.3 KB of information on 2 tracks (650 bytes each). The card information coding allowed great variations of the reading speed, due to manual handling.
The HP-IL (Interface Loop) interface allowed connecting as far as 30 peripherals simultaneously on the HP-75C. Amid the peripherals, one could find a display unit, printers, a modem, a tape recorder and all the HP-IL standard peripherals.
As always with HP, the manuals were very complete and pedagogical.
The HP-75D was released two years later. It added a wand and wand port. When used with the Bar Code ROM, the computer could scan CODE11, CODE39, UPC, and EAN codes. This made the computer useful for inventory control.