The HP-35 was

Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...

's first pocket calculator and the world's first ''scientific'' pocket calculator: a calculator with

trigonometric Trigonometry () is a branch of mathematics that studies relationships between side lengths and angles of triangles. The field emerged in the Hellenistic world during the 3rd century BC from applications of geometry to astronomical studies. ...

and

exponential function The exponential function is a mathematical function denoted by f(x)=\exp(x) or e^x (where the argument is written as an exponent). Unless otherwise specified, the term generally refers to the positive-valued function of a real variable, ...

s. It was introduced in 1972.

History

In about 1970 HP co-founder

Bill Hewlett William Redington Hewlett ( ; May 20, 1913 – January 12, 2001) was an American engineer and the co-founder, with David Packard, of the Hewlett-Packard Company (HP). Early life and education Hewlett was born in Ann Arbor, Michigan, where his ...

challenged his co-workers to create a "shirt-pocket sized HP-9100". At the time, slide rules were the only practical portable devices for performing trigonometric and exponential functions, as existing pocket calculators could only perform addition, subtraction, multiplication, and division. Introduced at , like HP's first scientific calculator, the desktop 9100A, it used

reverse Polish notation Reverse Polish notation (RPN), also known as reverse Łukasiewicz notation, Polish postfix notation or simply postfix notation, is a mathematical notation in which operators ''follow'' their operands, in contrast to Polish notation (PN), in wh ...

(RPN) rather than what came to be called "algebraic" entry. The "35" in the calculator's name came from the number of keys. The original HP-35 was available from 1972 to 1975. In 2007 HP announced the release of the "retro"-look HP 35s to commemorate the 35th anniversary of the launch of the original HP-35. It was priced at . The HP-35 was named an IEEE Milestone in 2009.

Description

The calculator used a traditional floating decimal display for numbers that could be displayed in that format, but automatically switched to

scientific notation Scientific notation is a way of expressing numbers that are too large or too small (usually would result in a long string of digits) to be conveniently written in decimal form. It may be referred to as scientific form or standard index form, o ...

for other numbers. The fifteen-digit LED display was capable of displaying a ten-digit mantissa plus its sign and a decimal point and a two-digit

exponent Exponentiation is a mathematical operation, written as , involving two numbers, the '' base'' and the ''exponent'' or ''power'' , and pronounced as " (raised) to the (power of) ". When is a positive integer, exponentiation corresponds to r ...

plus its sign. The display used a unique form of multiplexing, illuminating a single LED segment at a time rather than a single LED digit, because HP research had shown that this method was perceived by the human eye as brighter for equivalent power. Light-emitting diodes were relatively new at the time and were much dimmer than high-efficiency diodes developed in subsequent decades. The calculator used three "AA"-sized NiCd batteries assembled into a removable proprietary battery pack. Replacement battery packs are no longer available, leaving existing HP-35 calculators to rely on AC power, or their users to rebuild the battery packs themselves using available cells. An external battery charger was available, and the calculator could also run from the charger, with or without batteries installed. Internally, the calculator was organized around a serial ( 1-bit) processor chipset made under contract by Mostek, processing 56-bit

floating-point numbers In computing, floating-point arithmetic (FP) is arithmetic that represents real numbers approximately, using an integer with a fixed precision, called the significand, scaled by an integer exponent of a fixed base. For example, 12.345 can ...

, representing 14-digit BCD numbers. The calculator had a four-register

stack Stack may refer to: Places * Stack Island, an island game reserve in Bass Strait, south-eastern Australia, in Tasmania’s Hunter Island Group * Blue Stack Mountains, in Co. Donegal, Ireland People * Stack (surname) (including a list of people ...

(x, y, z and t), the "enter" key pushed the displayed value (x) down the stack. Any binary operation popped the top two registers and pushed the result. When the stack was popped, the t register duplicated into the z register.

Descendants

The HP-35 was the start of a family of related calculators with similar mechanical packaging: * The

HP-45 The HP-45 is the second scientific pocket calculator introduced by Hewlett-Packard, adding to the features of the HP-35. It was introduced in 1973 with an MSRP of US$395 (). Especially noteworthy was its pioneering addition of a shift key that ga ...

added many more features, including the ability to control the output format (rather than the purely automatic format of the HP-35). It also contained an undocumented timer feature. The timer worked, but was not accurate enough to use as a

stopwatch A stopwatch is a timepiece designed to measure the amount of time that elapses between its activation and deactivation. A large digital version of a stopwatch designed for viewing at a distance, as in a sports stadium, is called a stop clock. ...

due to lack of a

crystal oscillator A crystal oscillator is an electronic oscillator circuit that uses a piezoelectric crystal as a frequency-selective element. The oscillator frequency is often used to keep track of time, as in quartz wristwatches, to provide a stable clock ...

. * The

HP-65 The HP-65 is the first magnetic card-programmable handheld calculator. Introduced by Hewlett-Packard in 1974 at an MSRP of $795 (), it featured nine storage registers and room for 100 keystroke instructions. It also included a magnetic card re ...

added programmability, with program storage on magnetic cards. * The

HP-55 The HP-55 was a programmable handheld calculator; a lower-cost alternative to the HP-65. Introduced by Hewlett-Packard in 1975, it featured twenty storage registers and room for 49 keystroke instructions. Its outward appearance was similar to the ...

, a less expensive follow-on to the HP-65, provided storage for smaller programs, but didn't provide any external storage. The timer that was already present on the HP-45 was now crystal-controlled to achieve the needed accuracy and explicitly documented. * The

HP-67 The HP-67 is a magnetic card-programmable handheld calculator, introduced by Hewlett-Packard in 1976 at an MSRP of $450. A desktop version with built-in thermal printer was sold as the HP-97 at a price of $750. Marketed as improved successo ...

expanded on the programmability of the HP-65, and added fully merged keycodes. * The HP-80 and cheaper HP-70 provided financial, rather than scientific functions, such as future value and net present value. Follow-on calculators used varying mechanical packaging but most were operationally similar. The HP-25 was a smaller, cheaper model of a programmable scientific calculator without magnetic card reader, with features much like the HP-65. The

HP-41 The HP-41C series are programmable, expandable, continuous memory handheld RPN calculators made by Hewlett-Packard from 1979 to 1990. The original model, HP-41C, was the first of its kind to offer alphanumeric display capabilities. Later came ...

C was a major advance in programmability and capacity, and offered

CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSF ...

memory so that programs were not lost when the calculator was switched off. It was the first calculator to offer

alphanumeric Alphanumericals or alphanumeric characters are a combination of alphabetical and numerical characters. More specifically, they are the collection of Latin letters and Arabic digits. An alphanumeric code is an identifier made of alphanumeric c ...

capabilities for both the display and the keyboard. Four external ports below the display area allowed memory expansion (

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...

modules), loading of additional programs ( ROM modules) and interfacing a wide variety of peripherals including

HP-IL The HP-IL (''Hewlett-Packard Interface Loop''), was a short-range interconnection bus or network introduced by Hewlett-Packard in the early 1980s. It enabled many devices such as printers, plotters, displays, storage devices (floppy disk drives ...

("HP Interface Loop"), a scaled-down version of the HPIB/

GPIB Glycoprotein Ib (GPIb), also known as CD42, is a component of the GPIb-V-IX complex on platelets. The GPIb-V-IX complex binds von Willebrand factor, allowing platelet adhesion and platelet plug formation at sites of vascular injury. It is def ...

IEEE-488 IEEE 488 is a short-range digital communications 8-bit parallel multi-master interface bus specification developed by Hewlett-Packard as HP-IB (Hewlett-Packard Interface Bus). It subsequently became the subject of several standards, and is ...

instrument bus. The later HP-28C and HP-28S added much more memory and a substantially different, more powerful programming metaphor.

Calculator trivia

* The HP-35 was long and wide, said to have been designed to fit into one of William Hewlett's shirt pockets. * Was the first scientific calculator to fly in space in 1973. * HP-35 calculators were carried on the

Skylab 3 Skylab 3 (also SL-3 and SLM-2) was the second crewed mission to the first American space station, Skylab. The mission began on July 28, 1973, with the launch of NASA astronauts Alan Bean, Owen Garriott, and Jack Lousma in the Apollo command ...

and

Skylab 4 Skylab 4 (also SL-4 and SLM-3) was the third crewed Skylab mission and placed the third and final crew aboard the first American space station. The mission began on November 16, 1973, with the launch of Gerald P. Carr, Edward Gibson, and Wil ...

flights, between July 1973 and February 1974. * Is the first pocket calculator with a numeric range that covered 200 decades (more precise 199, ±10^±99). * The LED display power requirement was responsible for the HP-35's short battery life between charges — about three hours. To extend operating time and avoid wearing out the on/off slide switch, users would press the decimal point key to force the display to illuminate just a single LED junction. * The HP-35 calculated arithmetic, logarithmic, and trigonometric functions but the complete implementation used only 767 carefully chosen instructions (7670 bits). * One high quality feature of the HP-35 was its use of double-injected keys. Rather than printing the function on the key surface where it could wear off over time and use as with cheaper calculators, the keys were constructed with two colors of plastic, providing durable key top labels for the labeled keys. * Introduction of the HP-35 and similar scientific calculators by

Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...

soon thereafter signaled the demise of the slide rule among science and engineering students. Slide rule holsters rapidly gave way to "electronic slide rule" holsters, and colleges began to drop slide-rule classes from their curricula. * 100,000 HP-35 calculators were sold in the first year, and over 300,000 by the time it was discontinued in 1975—3½ years after its introduction.

References

External links