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HP-20S

From Alfawiki
Hewlett-Packard
IndustryElectronics, Computer hardware, Calculators
FoundedJanuary 1, 1939; 87 years ago (1939-01-01)
Headquarters
Palo Alto
,
United States
ProductsCalculators, Computers, Printers

The HP-20S (model F1890A) is a scientific calculator with algebraic programmable capabilities, manufactured by Hewlett-Packard between 1987 and 2000.

Belonging to HP's Pioneer lineup, the 20S was designed as an affordable option primarily for students, sharing its hardware platform with the HP-10B business calculator. In contrast to more advanced models like the 32S and 42S, the 20S provided more fundamental features and utilized infix notation instead of the Reverse Polish notation found in many other HP devices.

Although relatively straightforward, the 20S supports keystroke programming with a capacity of up to 99 program steps and includes ten memory registers.

Hardware

Introduced at the 1989 Consumer Electronics Show with a launch price of $50, the HP 20S set a new affordability standard for HP calculators. This was made possible through streamlined integration across research, development, and manufacturing processes. It was released simultaneously with the HP-10B, which targeted business users but shared identical hardware components.

The 20S adopts the same physical design and a 37-key keypad as other Pioneer series calculators. Its processor is an HP Saturn (Bert) microchip operating at 640 kHz. With just 256 bytes of RAM, it represents the entry-level tier within the Pioneer family.

Unlike higher-tier models that feature dot-matrix displays for navigating menus—such as the 22S, 32S, and 42S—the 20S is equipped with a simpler 12-digit seven-segment display. Access to advanced functions is provided via two shift keys that assign secondary and tertiary functions to nearly every button.

Initially, the shift keys were colored blue and orange; however, in a 1999 revision, these were updated to green and purple.

Critical evaluation

A 1994 assessment of calculators identified several drawbacks of the HP 20S:

  • The statistics functions overwrite multiple recall registers that are shared among various statistical operations.
  • Computing large factorials may lead to overflow errors.
  • Complex number support is limited; for instance, attempting to calculate <math alt="Square root of -1">\sqrt{-1}</math> triggers an error despite an included complex number program.

Nonetheless, the device received commendations for its computational accuracy—avoiding rounding errors typical in comparable models—and for its well-crafted user manual.

Program library

The 20S comes preloaded with six ROM-based programs addressing common mathematical problems, which users can load into RAM for execution and modification:

  • A - [ROOT] root-finding algorithm for solving f(x)=0
  • B - [INT] definite integral calculation using Simpson’s method
  • C - [CPL] operations involving complex numbers
  • D - [3 by 3] matrix calculations and linear equation solving
  • E - [qUAD] quadratic equation solver
  • F - [fit] curve fitting utilizing exponential, logarithmic, and power functions

HP highlighted this collection of programs as a significant advantage of the 20S model.

HP-21S

The HP 21S is a derivative of the 20S specifically optimized for statistical computations. HP intended this calculator to replace traditional statistical tables similarly to how the HP-35 supplanted trigonometric and logarithmic tables.

It retains most functionalities of the 20S, including keystroke programming and standard scientific operations, while adding dedicated statistical features such as:

  • Probability and distribution functions including factorials, permutations, and combinations
  • Statistical analysis involving two variables
  • Generation of random numbers
  • A unique built-in library focused on statistics-related programs

To accommodate these enhancements, certain features present in the 20S—like base arithmetic operations, unit conversions, and hyperbolic functions—were omitted from the 21S.

Libraries

See also

External links

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