HP-20S

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HP-20S
HP-20S.jpg
The HP-20S
TypeProgrammable scientific
ManufacturerHewlett-Packard
Introduced1989
Discontinued2000
Calculator
Entry modeInfix
Precision12 display digits (15 digits internally), exponent ±499
Display typeLCD seven-segment display
Display size1 line
CPU
ProcessorSaturn (Lewis)
Programming
Programming language(s)key stroke
Firmware memory10 KB of ROM
Program steps99
Other
Power supply3×1.5V button cell batteries (Panasonic LR44, Duracell PX76A/675A or Energizer 357/303)
Weight4.2 oz (120 g)
Dimensions148×80×15mm

The HP-20S (F1890A) is an algebraic programmable scientific calculator produced by Hewlett Packard from 1989 to 2000.

A member of HP's Pioneer series, the 20S was a low cost model targeted at students, using the same hardware as the HP-10B business calculator. Compared with the higher-end 32S and 42S scientific calculators, the 20S includes much more basic functionality. As a student calculator, it also uses infix notation rather than the Reverse Polish notation found in higher-end HP calculators.

Despite these limitations, the 20S is keystroke programmable, supporting up to 99 program lines of fully merged instructions and ten memory registers.

Hardware[]

The 20S has the same physical form factor and 37-key keypad as other models in the Pioneer series. However, while the higher end scientific models in the series were fitted with dot-matrix displays that allowed their functionality to be organized into menus (the 22S, 32S and 42S being examples), the 20S has only a more primitive 12-digit seven-segment display. Advanced functionality is therefore accessed by a pair of shift keys, with almost every key on the keypad assigned secondary and tertiary functions.

The initial design used blue and orange shift keys, but a visual refresh in 1999 changed the color scheme to green and purple.

Libraries[]

There are six libraries in the ROM, which could be loaded to RAM and used and edited as user programs.

  • A- [ROOT] finder, finds a root of f(x)=0
  • B- [INT] integral, calculates definite integral using Simpson method
  • C- [CPL] complex numbers manipulations
  • D- [3 by 3] matrix manipulations and line equations solver
  • E- [qUAD] quadratic equation solver
  • F- [fit] curve fitting, using exponential, logarithmic and power functions

HP-21S[]

HP-21S

The HP 21S is a variant of the 20S designed specifically for statistical calculations. The majority of the features of the 20S are still present, including keystroke programming support and the typical trigonometric, logarithmic and exponential functions found on most scientific calculators. However, the 21S has several features specifically to support statistical analysis:

  • Probability and distribution: factorial, permutation and combination functions.
  • Two variable statistical calculations
  • Random number generation
  • The built-in library contains statistical programs that differ to the programs included with the 20S.

To accommodate the extra functionality, the 21S sacrifices some of the 20S's functionality; specifically it does not support base arithmetic and unit conversions, along with hyperbolic functions.

Libraries[]

See also[]

External links[]

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