Hewlett-Packard HP-01 Calculator Watch

Thanks to revolutions in microelectronics and display technologies, watches became tiny wrist computers in the 1970s. Hewlett-Packard introduced the HP-01 calculator wristwatch in 1977. Dubbed a “wrist instrument,” it combined interacting technologies: the time functions of a watch (time of day, alarm, timer, stopwatch, date and calendar) could work with an electronic calculator and memory. A wearer might calculate and display a time zone change, determine the number of days between calendar dates, or compute the anticipated cost of a lengthy long-distance phone call.

Entering information on the watch involved tapping on 28 buttons, most often with a stylus stored in the watch strap. Four raised buttons provided the wearer with frequently used information--the time of day, date, alarm, or memory.

The watch featured a quartz crystal time standard and a red LED (light emitting diode) display. It required three batteries, one to power six integrated circuits and two to drive the display. To conserve the battery, the display automatically turned off after a set period.

Sold in fine jewelry stores, these watches were costly—initially $650 for the stainless steel model or $750 for the gold-filled model. A precursor to the smartwatches of the 21st century, the HP-01 did not sell well, and Hewlett-Packard scrapped plans for a follow-up HP-02.