1. The Classic Series (1972 - 1982)

HP 35 Scientific HP 35 (Version 1)
The first HP Calculator and the world's first calculator with transcendental functions (SIN, COS, TAN, LN, LOG). Introduced on February 1, 1972. So called because it had 35 keys. It was made by William Hewlett for the company's own engineers. It had to be small enough to fit in a shirt-pocket. Four different versions of this calculator were manufactured over the years. This one is Version 1, also known as Red Dot because of the whole to the right of the ON/OFF switch, which when shifted to ON, revealed a red dot.
Code name: N/A. Original price: $395
HP 35 Scientific HP 35 (Version 2)
This is the second version of the HP 35. The only difference is that the red dot was dropped as unnecessary. One could figure out that the calculator was on, when the display was on, so the red dot was dropped. This change happened fairly quickly, rendering the first release of the HP 35 rather read and highly collectable.
HP 35 Scientific HP 35 (Version 3)
This is the third version of the HP 35. The only difference is that the label on the bottom now reads "Hewlett Packard 35" instead of just "Hewlett Packard" to differentiate it from the other calculators introduced in the mean time by Hewlett Packard.
HP 35 Scientific HP 35 (Version 4)
This is the fourth version of the HP 35. On this version, the labels of the function keys are printed on the keys, instead of above them, as is customary with any calculator since then. The keys also changed size and became a bit more elongated, as opposed to square in the previous three versions. Square keys were an HP first - and quite the look, in my opinion.
 HP 35 Emulator: To operate a Java-based HP 35 (Version 4)
calculator now, please click here!
HP 80 Business HP 80 (Version 1)
HP's second calculator and the company's first Business Calculator. This was the first ever calculator to introduce a SHIFT key, hence doubling the available functions without increasing the number of keys. Introduced on February 1, 1973. On this calculator HP changed the key xy to yx to more properly integrate this function in HP's RPN logic. The ENTER key was labeled SAVE to avoid confusing business users. Code name: N/A. Original price:$395
HP 80 Business HP 80 (Version 2)
As with the HP 35, when more models were introduced, the label on the bottom of the calculator had to be changed to identify the model number. This is version 2 of the HP 80, showing the "80" on the label.
HP 45 Scientific HP 45
HP's third calculator and second scientific, basically improving on the HP 35. Also, the first scientific calculator with a yellow SHIFT key. Introduced on May 1, 1973. One unique feature was the calculator's built in timer, basically a stop watch that could be accessed by pressing RCL then CHS, 7 and 8 all three keys at once. Code name: Wizard. Original price: $395
HP 65 Scientific HP 65
Introduced on January 19, 1974. HP's fourth calculator, this was the first programmable model with many new functions, a built-in magnetic card reader, allowing users to save programs on cards for future use. This was the most expensive pocket calculator ever sold. It was used as a backup computer by American astronauts during the Apollo missions. In one of those missions in outer space, the astronauts used the HP 65 to calculate course correction maneuvers during the rendezvous of the US Apollo and the Russian Soyuz spacecraft.
Code name: Superstar. Original price: $795
HP 70 Business HP 70
HP's second Business Calculator. HP called this one a Financial calculator, as opposed to the HP 80, which was sold as a Business calculator. It basically had fewer functions than the 80. The SAVE key was now renamed back to ENTER. Introduced on August 1, 1974 and was withdrawn a year later. Due to its unpopularity, this is one of the rarest ones to find.
Code name: Scrooge. Original price:$275
HP 55 Scientific HP 55
HP's sixth calculator, it was introduced on January 1, 1975 as a cheaper alternative to the HP 65. It had no card reader, fewer steps and fewer mathematical functions. However, it included a series of conversion functions. It included a stopwatch function that made it rather unique among the classics (the 45 had a timer, but it was hidden). Code name: Merlin. Original price: $395
HP 67 Scientific HP 67
This was essentially an upgraded HP 65, but with many more features requiring the addition of a third black shift key (h). It was the last calculator of the Classic Series, introduced on July 1, 1976 and on sale for 6 years .
Code name: Hawkeye. Original price: $450
This calculator was a gift from...

Click on the images for a larger picture.
Click on the for a picture of the manual's front cover.

Up Next

Copyright A. Spyropoulos 2005-2008