Hewlett Packard
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Model: HP-19C
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Year: 1977-1979
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Info: The HP-19C and HP-29C were scientific/engineering pocket calculators made by Hewlett-Packard between 1977 and 1979. They were the most advanced and last models of the "20" family (compare HP-25) and included Continuous Memory (battery-backed CMOS memory) as a standard feature.
The HP-19C included a small thermal printer, one of the very few hand-held scientific calculators to offer such a feature (HP-91, HP-92 and HP-97 were desktop units and later models like the HP-41C only supported external printers). Due to the printer's power requirements, the 19C used a battery pack of four AA-sized NiCd cells, adding to the weight of the calculator and printer mechanism.
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The coolest thing we have with the HP-19C is having the HP logo at the point used as a comma by the calculator. A special thanks goes to Alessandro (alexanderpentagon) who helps me with the HP.
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Model: HP-21
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Year: 1975-1978
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Info: The HP-21 was a scientific calculator produced by Hewlett-Packard between 1975 and 1978. It was designed as a replacement for the HP-35, and was one of a set of three calculators, the others being the HP-22 and HP-25, which were similarly built but aimed at different markets.
As with most HP calculators then and now, the HP-21 used RPN entry logic, with a four-level stack. It also had a single user-accessible memory register. As was normal at the time, memory was not preserved on power-down. A physical slider switch toggled between degrees and radians modes, which was an unusual feature. It had a 12-digit LED display, which was less than the 15 digits of the HP-35. Because of these fewer digits the HP-21 (and similar calculators such as the HP-25) could display 10-digit floating point numbers but only an 8-digit mantissa with a 2-digit exponent when scientific notation was used. A shift key provided access to functions whose legends were printed on the fronts of the tall trapezoidal keys.
Model: HP-25
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Year: 1975/1978
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Info: The HP-25 was a hand-held programmable scientific/engineering calculator made by Hewlett-Packard between early January 1975 and 1978. The HP-25 was introduced as a cheaper (US$195 MSRP) alternative to the ground-breaking HP-65.
Model: HP-35
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Year: 1972
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Info: The HP-35 was Hewlett-Packard's first pocket calculator and the world's first scientific pocket calculator: a calculator with trigonometric and exponential functions. It was introduced in 1972
Wikepedia HP-35 HP-35 Simulator
Model: HP-38 E
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Year: 1978
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Info: The HP-38C and HP-38E were the high-end business members of the 30 series. The HP-38E was introduced first, followed a year later by the HP-38C which added continuous memory.
.jpg "Olivetti Valentine")
