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Hewlett Packard HP-01 Calculator Wristwatch

Updated 5/11/2022


While this instrument is somewhat outside the Old Calcualtor Museum's range of interest as far as calculators go, the Hewlett Packard HP-01 is such an amazing and absolutely (excuse the cliche') cool device that when the rare opportunity came up for the museum to acquire one, the opportunity was seized immediately.

The HP-01 is yet another example of the ability of Hewlett Packard to stretch the state of the art way beyond that of the time (1977). Starting with the amazing HP 9100 all-transistor, programmable scientific calculators, through the breakthrough HP-35 handheld scientific calculator, Hewlett Packard always seemed to find a way to make the seemingly impossible happen...and do it right, without much in the way of compromise, and with very high quality.

The HP-01 combines the function of a very accurate timepiece, alarm clock, calendar, calculator, stopwatch, and timer all into one compact (for the time, anyway - by today's standards it's positively bulky) and wearable At the time, the notion of being able to cram all of these functions into a device that one could wear on their wrist was that of science fiction. Given the experience that HP had with miniaturizing electronics, the development of such a device seemed like a great challenge to the engineers tasked with the project, and they came through with flying colors.

Two versions of the HP-01 were made, one with a gold filled body and gold-plated stainless-steel band, and the other with a stainless steel body and band. The only difference was the case and band; functionally the two versions were identical. The HP-01 sold to those with sufficient wealth for the $795 (roughly $3,800 in 2022 dollars) required to buy the gold version, or $695 for the stainless steel version.

The HP-01 was quite a hit with the high-roller technology execs of the day, and they sold well through their discontinuation in 1980, by which time, liquid-crystal display technology had made expensive and power-hungry LED display watches difficult to sell. Hewlett Packard opted not to continue in the wearable calcualtor/watch business after the HP-01 was discontinued, although some prototypes for a next-generation HP-01 were developed, but shelved. .

The HP-01 has a tiny keyboard built into the face of the instrument, and a 9-digit LED display behind a red display panel. The LED display is only activated when necessary, shutting itself off after about 2 seconds with no keypress in all but stopwatch mode to conserve battery power. The commonly used keys on the keyboard (e.g., those that recall the time, date, memory register, alarm register, or activate the stopwatch functions) are slightly raised to provide easy access with a fingertip. The lesser used keys are recessed slightly, such that a stylus (or, as commonly used, a pencil point or other such unsuitable device) could be used to depress them. A small stylus clips into the watchband clasp, which is relatively easy to remove and use. The HP-01 also came with a pencil-like stylus, which, unfortunately, was commonly lost. (If you know of the whereabouts of one of these, the museum would be interested in acquiring it -- please contact us via EMail.)

Logic Block Diagram of HP-01 Logic. Note 9 or 12-digit capability in chipset

This instrument was capable of a vast number of functions, many of which today's sophisticated calculators don't provide. Most notable of the specialized functions of the HP-01 is the full 200-year calendar (Y2K-compliant, by the way!) going from 1900 through 2099. The calculator has the ability to do date arithmetic, (for example, calculating the number of days between any given two dates), as well as adding or subtracting a given number of days from an arbitrary date. It can also provide the day of the week or day of the year for any given date. The calculator can also do time calculations in much the same way as date calculations. (For example, you can recall the current time, add 2:15:00 (2 hours, 15 minutes, 0 seconds) to it, then set the HP-01's alarm with the result). The HP-01 also contains a stopwatch function, capable of .01 second resolution. The stopwatch can also do split functions, and also allows a special mode, useful for calculating costs of services which are charged by time. In this mode, the calculator will update the current accumulated cost on a second by second basis as the stopwatch runs. This feature was considered useful for determining the running cost of long-distance telephone calls (which people actually cared about back in those days, as long-distance calls could get quite expensive). The stopwatch can also be used as a countdown timer. A time interval can be entered and the stopwatch started. The time will count down until 00:00:00 is reached, at which the calculator's alarm tone will sound. The calculator provides the basic four math functions and percent, along with functions for converting time between decimal and HH:MM:SS form (e.g., 8.25 = 8:15:00) and back. A memory is provided, into which any form of data (date, time, time interval, or number) can be stored and recalled.

The calculator functions have a range of -9.999x1099 to 9.999x1099, with the display automatically switching to scientific notation when the number can not be displayed in floating decimal mode. In floating decimal mode, the left-most digit of the display is reserved for sign (blank if positive, '-' if negative), and the remaining digits are used for number display. The decimal point requires a full digit position to display, meaning that the maximum display content in floating decimal mode is -9999999. The calculator operates in algebraic mode (in contrast to most HP calculators, which operate using the Reverse-Polish Notation method), and has full floating decimal point. If an error occurs (for example, division by zero), the display blinks to notify the user of the error, requiring a press of the [C] (clear) key to resume normal operation. The calculator is not particularly quick at generating results, with 9999999 divided by 1 taking approximately one second to complete. Considering that six complex chips and an LED display had to be crammed into such a small space, including three button-cell batteries to power it, it's no wonder that HP's engineers had to compromise a bit on speed in favor of low power consumption.

For much more detailed information about the HP-01, please hop over to Dave Hicks' wonderful Museum of HP Calculators site. To go directly to the HP-01 page there, click HERE. More information about the design of the HP-01 can also be found in the US Patent (US #4158285A) filed in February, 1976 for this amazing device.


Text and images Copyright ©1997-2022, Rick Bensene.