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HP-35

From Alfawiki
HP-35
Company typeProduct
IndustryElectronics, Calculators
Founded1972; 54 years ago (1972)
FounderBill Hewlett (commissioned development)
ProductsScientific calculator
ParentHewlett-Packard

The HP-35 represented Hewlett-Packard’s inaugural pocket calculator and was recognized as the first scientific calculator compact enough to fit in a pocket. It incorporated advanced features such as trigonometric and exponential functions, debuting in 1972.

History

In the early 1970s, specifically around 1970, HP co-founder Bill Hewlett commissioned France Rode to develop a compact version of the HP-9100 that could fit in a shirt pocket. Prior to this, portable devices capable of trigonometric and exponential computations were limited to slide rules, while existing handheld calculators only performed basic arithmetic operations. When unveiled at , the HP-35 delivered scientific functionality comparable to the desktop 9100A, but utilized reverse Polish notation (RPN) rather than traditional algebraic input. Its designation derived from the total number of keys—35.

The original HP-35 remained on the market between 1972 and 1975. To commemorate its 35th anniversary, HP introduced the "retro" styled HP 35s in 2007, retailing at .

In 2009, the HP-35 received recognition as an IEEE Milestone.

Description

Equipped with a fifteen-digit LED display, the HP-35 could present a ten-digit mantissa alongside a sign and decimal point, plus a two-digit signed exponent, automatically switching to scientific notation when appropriate. Its distinctive multiplexed LED system illuminated one segment at a time, improving perceived brightness while conserving energy. However, early LED technology limited display luminosity compared to later advancements.

The device was powered by three "AA" NiCd cells housed in a proprietary removable pack; since replacements are no longer produced, users typically operate it via AC power or through custom battery refurbishments. An external charger facilitated use both with and without batteries installed.

Internally, the calculator operated using a serial (1-bit) processor chipset manufactured by Mostek and American MicroSystems Inc. It handled decimal floating-point numbers consisting of a 10-digit mantissa and 2-digit exponent stored in a 56-bit binary-coded decimal (BCD) format that included sign nibbles.

HP-35 functions
Arithmetic Addition (+), subtraction (−), multiplication (×), division (÷)
Trigonometry Sine (sin), arcsine (arc sin); cosine (cos), arccosine (arc cos); tangent (tan), arctangent (arc tan) — all in decimal degrees
Logarithms Base-10 logarithm (log10 x), natural logarithm (loge x), exponential function (ex)
Other Reciprocal (1/x), square root (√x), power function (xy), constant (π)

The calculator utilized a four-level register stack labeled x, y, z, and t for its calculations. Pressing the "enter" key pushed values upward through the stack; binary operations removed two values from the stack and then pushed the result back onto it. The stack functioned as a circular buffer with a “roll down” feature allowing cycling through registers.

Descendants

The HP-35 laid the foundation for a series of calculators sharing similar physical designs:

  • The HP-45 expanded capabilities by adding manual control over output formatting and included an undocumented timer feature that was not precise enough for stopwatch use.
  • The HP-65 introduced programmability with magnetic card storage for programs.
  • The HP-55, positioned as a more affordable alternative to the HP-65, supported smaller programs without external storage and incorporated a crystal-controlled timer.
  • The HP-67 enhanced programmability further by implementing fully merged keycodes.
  • The HP-70 and HP-80 models focused on financial computations such as calculating future value and net present value.

Subsequent models varied mechanically but preserved operational consistency. The HP-25 was a compact programmable scientific calculator lacking magnetic card support. The HP-41C advanced programmability through CMOS memory that retained data after power-off, featured an alphanumeric display and keyboard, and offered four external ports for memory expansion (RAM), program loading (ROM), and peripherals including the HP-IL, an instrument bus interface. Later models like the HP-28C and HP-28S provided increased memory capacity along with enhanced programming functionality.

Calculator trivia

  • Measuring approximately long and wide, the HP-35 was crafted to conveniently fit inside William Hewlett's shirt pocket.
  • It holds the distinction of being the first scientific calculator to operate in space, utilized during the Skylab 3 and Skylab 4 missions from July 1973 through February 1974.
  • The device supported a numeric range spanning 200 decades, equivalent to ±10^±99.
  • Due to its LED display, battery life was limited to roughly three hours; users could prolong usage by activating only one LED at a time using the decimal point key.
  • With just 767 instructions (7,670 bits), the calculator was capable of executing arithmetic, logarithmic, and trigonometric calculations.
  • The keys featured high-grade double-injection molding, ensuring that labels remained legible and resistant to wear, unlike the printed labels found on less expensive calculators.
  • The launch of the HP-35, soon followed by similar offerings from Texas Instruments, swiftly rendered slide rules obsolete for science and engineering students.
  • More than 100,000 units were sold within the first year, with total sales surpassing 300,000 by the time production ceased in 1975, only three and a half years after its debut.

See also

Further reading

External links

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