HP-35
Encyclopedia
Hewlett-Packard
Hewlett-Packard Company or HP is an American multinational information technology corporation headquartered in Palo Alto, California, USA that provides products, technologies, softwares, solutions and services to consumers, small- and medium-sized businesses and large enterprises, including...
's first pocket calculator and the world's first scientific pocket calculator (a calculator with trigonometric and exponential function
Exponential function
In mathematics, the exponential function is the function ex, where e is the number such that the function ex is its own derivative. The exponential function is used to model a relationship in which a constant change in the independent variable gives the same proportional change In mathematics,...
s). Like some of HP's desktop calculators it used reverse Polish notation
Reverse Polish notation
Reverse Polish notation is a mathematical notation wherein every operator follows all of its operands, in contrast to Polish notation, which puts the operator in the prefix position. It is also known as Postfix notation and is parenthesis-free as long as operator arities are fixed...
. Introduced at US$395, the HP-35 was available from 1972 to 1975.
Market studies at the time had shown no market for pocket sized calculators. In about 1970, HP co-founder Bill Hewlett
William Reddington Hewlett
William Redington Hewlett was an engineer and the co-founder, with David Packard, of the Hewlett-Packard Company . He was born in Ann Arbor, Michigan where is father taught at the Univerisy of Michigan Medical School...
challenged his co-workers
France Rode
France Rode is an engineer and inventor best known for his work on the HP-35 pocket calculator. He was one of the four lead engineers at Hewlett-Packard assigned to this project....
to create a "shirt-pocket sized HP-9100". Thus, the first approximately 12 HP-35 portable calculators were made as a "hack" by and for other engineers at HP. It is rumored that the development engineer got carried away and implemented a full suite of scientific functions to satisfy requests from his co-workers. When these prototypes proved popular, HP decided to turn the HP-35 into a commercial product. The HP-35 was the first calculator with a full suite of trigonometric and transcendental functions.
In the first months orders were exceeding HP's expectations as to the entire market size, which was 10,000 units per year. Before the HP-35, the only practical portable devices for performing trigonometric and exponential functions were slide rule
Slide rule
The slide rule, also known colloquially as a slipstick, is a mechanical analog computer. The slide rule is used primarily for multiplication and division, and also for functions such as roots, logarithms and trigonometry, but is not normally used for addition or subtraction.Slide rules come in a...
s. Existing pocket calculators at the time were only four-function, i.e., they could only do addition, subtraction, multiplication, and division. It had been originally known simply as "The Calculator", but Hewlett suggested that it be called the HP-35 because it had 35 keys.
On July 12, 2007, HP announced the release of the "retro"-look HP 35s
HP 35s
The HP 35s Scientific Calculator is, as of 2007, the latest in Hewlett-Packard's long line of non-graphing scientific and programmable calculators...
in commemoration of the original HP-35 .
The HP-35 was named an IEEE Milestone in 2009.
Description
Scientific notation
Scientific notation is a way of writing numbers that are too large or too small to be conveniently written in standard decimal notation. Scientific notation has a number of useful properties and is commonly used in calculators and by scientists, mathematicians, doctors, and engineers.In scientific...
for other numbers. The fifteen-digit LED
Light-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
display was capable of displaying a ten-digit mantissa
Significand
The significand is part of a floating-point number, consisting of its significant digits. Depending on the interpretation of the exponent, the significand may represent an integer or a fraction.-Examples:...
plus its sign and a decimal point and a two-digit exponent
Exponentiation
Exponentiation is a mathematical operation, written as an, involving two numbers, the base a and the exponent n...
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.
The calculator used three "AA"-sized NiCd batteries
Nickel-cadmium battery
The nickel–cadmium battery ' is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes....
assembled into a removable proprietary battery pack. Replacement battery packs are no longer available, leaving existing HP-35s 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 (one-bit) processor chipset
Chipset
A chipset, PC chipset, or chip set refers to a group of integrated circuits, or chips, that are designed to work together. They are usually marketed as a single product.- Computers :...
made under contract by Mostek
Mostek
Mostek was an integrated circuit manufacturer, founded in 1969 by ex-employees of Texas Instruments. Initially their products were manufactured in Worcester, Massachusetts, however by 1974 most of its manufacturing was done in the Carrollton, Texas facility on Crosby Road...
, processing 56-bit floating-point number
Floating point
In computing, floating point describes a method of representing real numbers in a way that can support a wide range of values. Numbers are, in general, represented approximately to a fixed number of significant digits and scaled using an exponent. The base for the scaling is normally 2, 10 or 16...
s, representing 14-digit BCD
Binary-coded decimal
In computing and electronic systems, binary-coded decimal is a digital encoding method for numbers using decimal notation, with each decimal digit represented by its own binary sequence. In BCD, a numeral is usually represented by four bits which, in general, represent the decimal range 0 through 9...
numbers.
Descendants
The HP-35 was the start of a family of related calculators which all shared similar mechanical packaging:- The HP-45HP-45The HP-45 was the second scientific calculator introduced by Hewlett-Packard, adding to the features of the HP-35. Especially noteworthy was its pioneering addition of a shift key that gave the other keys alternate functions....
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 stopwatchStopwatchA stopwatch is a handheld timepiece designed to measure the amount of time elapsed from a particular time when activated to when the piece is deactivated. A large digital version of a stopwatch designed for viewing at a distance, as in a sports stadium, is called a stopclock.The timing functions...
due to lack of a crystal oscillatorCrystal oscillatorA crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency...
. - The HP-65HP-65The HP-65 was 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 reader/writer to save and load programs...
added programmability, with program storage on magnetic cards. - The HP-55HP-55The 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 identical to the HP-65, except that a few key functions were...
, 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 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
HP-25
The HP-25 was a hand-held programmable scientific/engineering calculator made by Hewlett-Packard between 1975 and 1978. The HP-25 was introduced as a cheaper alternative to the ground-breaking HP-65....
was a smaller, cheaper model of a programmable scientific calculator without magnetic card reader, with features much like the HP-65. The HP-41C
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...
was a major advancement in programmability and offered CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
memory so that programs were not lost when the calculator was switched off. It was the first calculator to offer alphanumeric
Alphanumeric
Alphanumeric is a combination of alphabetic and numeric characters, and is used to describe the collection of Latin letters and Arabic digits or a text constructed from this collection. There are either 36 or 62 alphanumeric characters. The alphanumeric character set consists of the numbers 0 to...
capabilities for both the display and the keyboard. Four external ports below the display area allowed memory expansion (RAM
Ram
-Animals:*Ram, an uncastrated male sheep*Ram cichlid, a species of freshwater fish endemic to Colombia and Venezuela-Military:*Battering ram*Ramming, a military tactic in which one vehicle runs into another...
modules), loading of additional programs (ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
modules) and interfacing a wide variety of peripherals including HP-IL
HP-IL
The HP-IL , was a short-range interconnection bus or network introduced by Hewlett-Packard in the early 1980s. It enabled several devices such as printers, floppy disk drives, tape readers, etc...
("HP Interface Loop"), a scaled-down version of the HPIB/GPIB/IEEE-488
IEEE-488
IEEE-488 is a short-range digital communications bus specification. It was created for use with automated test equipment in the late 1960s, and is still in use for that purpose. IEEE-488 was created as HP-IB , and is commonly called GPIB...
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 5.8 inches (147.3 mm) long and 3.2 inches (81.3 mm) wide, said to have been designed to fit into one of William Hewlett's shirt pockets.
- Is the first scientific calculator to fly in space (along with the HP-65HP-65The HP-65 was 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 reader/writer to save and load programs...
and HP-41HP-41The 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...
) in 1972 - Is the first pocket calculator with a numeric range that covered 200 decades (10+/-100)
- 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 trigonomic functions but the complete implementation used only 767 carefully chosen instructions (7670 bits).
- Introduction of the HP-35 and similar scientific calculators by Texas InstrumentsTexas InstrumentsTexas Instruments Inc. , widely known as TI, is an American company based in Dallas, Texas, United States, which develops and commercializes semiconductor and computer technology...
soon thereafter signaled the demise of the slide rule as a status symbol 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.
- In 2007, HP introduced a revised HP 35sHP 35sThe HP 35s Scientific Calculator is, as of 2007, the latest in Hewlett-Packard's long line of non-graphing scientific and programmable calculators...
calculator in memory of the original. - An emulation of the HP-35 is available for the Apple iPadIPadThe iPad is a line of tablet computers designed, developed and marketed by Apple Inc., primarily as a platform for audio-visual media including books, periodicals, movies, music, games, and web content. The iPad was introduced on January 27, 2010 by Apple's then-CEO Steve Jobs. Its size and...
.
External links
- The Museum of HP Calculators' article on the HP-35
- HP Journal, June 1972
- HP-35 pictures on MyCalcDB (database about 70's and 80's pocket calculators)
- A thorough analysis of the HP-35 firmware including the Cordic algorithms and the bugs in the early ROM.
- Tom Osborne’s Story in His Own Words - the invention of the HP 9100, HP 35 and HP 65