Professionally and fully repaired HP97. Comes with carrying case.
We have two units of HP97 that have been professionally repaired. The gummy wheel of the card reader has been replaced, and the gear of the printer has been changed. The cylinders that carry the paper have been filed and moistened. The machine has been cleaned and tested.
The machine comes with a new battery and the 230v original power supply, as well as the carrying case.
The 67/97 provide a complete set of scientific, statistical and engineering operations, including trigonometrical, logarithmic and exponential functions, coordinate conversions, average/deviation etc.
The HP-67/97 series featured a program memory of 224 eight-bit words. The two extra bits per word compared to the HP-65's six allowed the designers to store any program instruction in a single memory cell ("fully merged keycodes") even if it required multiple keystrokes to enter (see image). Programs could include 20 labels, subroutines (3 levels deep), four flag registers, 8 comparison functions, and extended index and loop control functions.
At 15 digits, the display was wider than those of the predecessor models, although the decimal point was displayed on its own digit position. The HP-67 keys carry up to four functions each, accessed through "f", "g" and "h" prefix keys (gold, blue and black labels, respectively). The model 97 had more (and larger) keys, therefore only two functions were assigned to each key. When interchanging magnetic cards between the HP-67 and the HP-97, the calculators' software took care of converting the key codes, and emulated the 97's print functions through the 67's display.
The HP-67 is powered by a pack of three AA-sized nickel-cadmium rechargeable batteries. Owing to the power requirements of the built-in thermal printer, the HP-97 employs a larger battery pack and more powerful charger.
Memory and programming
Of the 26-register data memory, the first ten ("primary registers") could be accessed directly, ten more as an alternate register set, and the remaining six had special functions for statistical operations and as an index register. Using the latter, a program could access all 26 registers as a single indexed array. Data memory is not permanent as in later models, i.e. register contents and program are lost when powering off.
The built-in magnetic card reader/writer could be used to save programs and data, with the ability to combine data from multiple cards. The same magnetic card format was later used for the HP-41C which offered compatibility to the 67/97 through software in the card reader. HP offered a library of programs supplied on packs of pre-recorded magnetic cards for many applications including surveying, medicine, as well as civil and electrical engineering.