HP-21
| Industry | Electronics, Computer hardware |
|---|---|
| Founded | January 1, 1939 |
| Headquarters | Palo Alto, California , United States |
| Products | HP-21 scientific calculator |
The HP-21 was a scientific calculator manufactured by Hewlett-Packard between 1975 and 1978. It served as the successor to the HP-35 and was introduced alongside the HP-22 and HP-25, forming a series aimed at various user groups.
Utilizing RPN input with a four-level stack, the HP-21 included a single memory register accessible to users. Its memory contents were lost when the device was powered off. A notable feature for its era was a manual slider switch that enabled users to select between degrees and radians modes. The calculator displayed numbers on a 12-digit LED screen, fewer than the 15 digits available on the HP-35, which restricted scientific notation to an 8-digit mantissa plus a 2-digit exponent. Secondary functions were accessible through a shift key, with these functions indicated on the keys themselves.
During its development phase, the HP-21 was known by the codename Pumpkin and was part of Hewlett-Packard's Woodstock lineup. The retail price in the United States decreased from $125 at launch in 1975 to $80 by 1978.
A modified variant featuring an additional rear-facing display was produced by Educational Calculator Devices under the name EduCALC 21 GD.