HP 25


Scientific Calculator

"Introduced on August 1 1975, six months after the HP-21, this was the eighth equal (with the HP-22) handheld electronic calculator sold by HP, and the first really powerful yet small technical model - the same size as the HP-21 but with more functions, and programmable to boot... Its codename, "Squash", might be an allusion to the amount of functionality squashed into such a small package" Wlodek Mier-Jedrzejowicz.
Source: MoHPC - The Museum of HP Calculators

X-Number World