HP-35

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HP-35 pocket calculator (1972)

With its first pocket calculator HP-35 , Hewlett-Packard brought the world's first technical and scientific pocket calculator with trigonometric , logarithmic and exponential calculation functions onto the market in 1972 . Contrary to HP's expectations, the device became a great sales success and heralded the end of the mechanical slide rule as a standard calculation tool, which was still widely used in science and industry at the time . It was the first in a long line of mostly programmable pocket calculators from the company.

On July 12, 2007, Hewlett-Packard launched the successor model, the HP 35s , for the 35th anniversary .

Development history

Before the HP-35, slide rules and table books were the only practical arithmetic tools for trigonometric and exponential arithmetic functions. The electronic pocket calculators that were already in existence at that time could only do the four basic arithmetic operations .

Contemporary market surveys did not reveal the need for a pocket calculator; Nevertheless, HP co-founder Bill Hewlett started the development of a “ pocket-sized Hewlett-Packard 9100A ”, and the marketing prognoses soon proved to be wrong: in the first few months, the number of orders exceeded HP's expectations of the total needs of the market.

When the HP-35 was launched in the US , the retail price was 395 US dollars , which, based on today's purchasing power , would correspond to around 2,400 US dollars. This model was produced from 1972 to 1975 in slightly different design variants.

technology

Electronics board of the HP-35

As with the desktop calculator HP-9100, the reverse Polish notation (UPN) was selected for input on the HP-35 . Therefore, the HP-35 does not offer a key with the equal sign =at the end of an arithmetic operation , as is usually the case today , but a Enterkey to separate the input of the arithmetic operands to be entered one after the other. The arithmetic process is triggered by pressing the desired arithmetic operation key immediately after entering the second operand. The stack has been expanded to four levels, but the top level (T) is also used for trigonometric functions.

The computer used the conventional floating point display for numbers that could be displayed with it, but automatically switched to the scientific exponential display for larger or smaller numerical values ​​that could no longer be displayed in floating point format. The 15-digit LED display could show a 10-digit mantissa and a 2-digit decimal exponent , each with a sign . In a multiplex process, the individual LED segments of the display were lit up one after the other instead of the complete seven-segment digits , as was previously the case , as studies at HP had shown that this gave the human eye a brighter overall impression with the same power consumption.

A battery pack consisting of three NiCd cells the size of mignon cells and an external plug-in power supply / charger, which can also be used without an inserted battery pack, were used to supply energy .

The internal calculation methods use 14-digit BCD numbers, which are processed by the 1-bit serially working chipset using a 56-bit floating point representation.

successor

HP-35s Calculator (2007)

The HP-35, produced from 1972 to 1975, was the beginning of a family of related pocket calculators with a very similar housing design:

  • The HP-80 , HP's second pocket calculator, produced from 1973 to 1978, specialized in financial mathematical functions. As a cheaper alternative, the HP-70 , with its reduced functionality, was offered from 1974 to 1975 .
  • The HP-45 , produced from 1973 to 1976, was (still with 35 keys) expanded by the introduction of a second function key αfor the first time compared to the HP-35 with additional functions, including the possibility to set the display format manually instead of automatically. The firmware contained a stopwatch as an undocumented function, but it worked very imprecisely due to the lack of crystal stabilization of the clock frequency.
  • The HP-65 , produced from 1974 to 1977, was the world's first programmable pocket calculator and for the first time came close to Bill Hewlett's specification of a "pocket-sized HP-9100". Remarkably, the HP-65 already had an external storage medium in the form of an integrated magnetic card reader for the programs comprising up to 100 program steps, offered a program sequence control with conditional branches and program loops and flag control, as well as keys Aup to which could be redefined by the user software E. This model also had only 35 keys, but with up to four times multiple assignments.
  • The HP-55 , produced from 1975 to 1977, was a cheaper sister model of the HP-65, without a magnetic card reader and with reduced program memory. The quartz oscillator built into the HP-55 allowed the officially documented use of the stopwatch function already installed in the HP-45.
  • The HP-67 , produced from 1976 to 1982 with the new technology of the so-called twenties series (HP-21, HP-22, HP-25, HP-29C), offered more program and data memory and various functional improvements compared to the HP -65.
  • The successor model, the HP 35s, launched in 2007 for the 35th anniversary, is a programmable scientific pocket calculator that can be operated either algebraically or in reverse Polish notation. It has an equation solver, numerical integration and 32 KB memory. The manufacturer is the Taiwanese Kinpo .

Trivia

  • Originally the new device was just supposed to be called The Calculator , but Bill Hewlett suggested the HP-35 because of its 35 keys .
  • The HP-35 was exactly 5.8 inches long and 3.2 inches wide, just like Bill Hewlett's shirt pocket, hence the name calculator.
  • Because of the energy-hungry LED display, a single charge with the low battery capacity available at the time (approx. 450 mAh) only lasted approx. Three hours. However, in order to avoid wear and tear on the on / off switch due to frequent switching, electricity was saved simply by pressing the decimal point key during pauses in the calculation; because as a result, only a single decimal point on the LED display was lit.
  • The complete implementation of the arithmetic, logarithmic and trigonometric functions of the HP-35 comprised 767 cleverly programmed command steps with a command word length of ten bits each (= 7670 bits). The three ROM modules, each with 256 10-bit words of the bit-serial computer, are the round metal housings with only ten pins each in the middle of the motherboard; today an unusual design for ICs.
  • The introduction of the HP-35, and soon similarly powerful scientific calculators from Texas Instruments , quickly led to the replacement of the slide rule as a status symbol among science and engineering students by electronic pocket calculators. Courses on the use of slide rules disappeared from the curriculum.
  • The HP-35 was the first scientific calculator to be used in space aboard Skylab in 1973 . The programmable HP-65 followed later for this purpose

Web links

(all in English)

Commons : HP-35  - collection of pictures, videos and audio files

Individual evidence

  1. ↑ Press release from HP on the market launch of the HP 35s
  2. ↑ HP-65 in space