HP 20S: On the left is the later keyboard, which has the dark green and pink shift buttons, the one on the right has the earlier keyboard with blue and orange keyboard. The latter was given to me by Jason Foose and it is much appreciated!
Retro: HP 20S
This is a keystroke programmable Helwett Packard calculator. What is unusual for a keystroke programmable calculator is that the HP 20S is algebraic rather than RPN. The tell-tale sign is that the HP 20S has an equals key rather than an ENTER key.
There is an impressive set of scientific functions which include trigonometry, logarithms, exponential functions, four metric/English conversions, percent change, integer and fraction parts, degree/radian conversion functions, polar/rectangular conversion, combination, permutation, factorial (of integers only), sexadecimal conversions, absolute value, and standard linear regression.
As far as the programming is concerned, we get 99 steps with two tests: x≤y? (Hidden register ≥ display value? ) and x=0?, and unconditional transfers. Six dedicated labels, A - F, are included. A big feature with the HP 20S is that you can load six built in programs that are always available. Just press [ left shift ], [ delete key ] (LOAD), to get access to:
A: root finder
B: numeric integral
C: complex number arithmetic
D: 3 x 3 matrices, including determinant
E: quadratic equation solver
F: exponential, logarithmic, power regression
The HP-20S was in production for over 15 years before ceasing production in 2003.
Thank you Jason Foose for the blue/orange keyboard. :)
This blog is property of Edward Shore. 2014