commodore pr100

this model was one of two programmables produced by commodore in 1977.

similar in style to the p50 but with a few more functions and extra program memory, the pr100 has 10 memories and 72 program steps. unfortunately, the steps are recorded keystrokes so that `f' or (inv) keys equire storage and goto xx is 3 steps.

there are 45 keys which is sufficient for most functions to be on their own. the presence of an inv key means that some functions like e^x and 10^x could have been expressed as inv ln and inv log. the display is quite nice with 8+2 led, the 6's and 9's look unusual today and the exponent digits are tastefully reduced in size.

the unit is powered internally by 3 rechargeable AA cells (not removable), or the external mains adapter which is 6v. (note: if the internal cells are dead and are removed, use a separate 4.5v dc supply not the original).

there is no algebraic precedence (lame) and parentheses work to four levels with no implied multiply. otherwise there is a good scientific function set including hyperbolics, 2d stats with regression slope and intercept, unit conversions and combinations and permutations. the latter work in a peculiar way using m9. for example to calculate 52c13; type 13 m 9 52 Cnm.

programming is effected by a mode switch to either of clear, load or run. in clear mode, memory locations can be overwritten by nop or the whole program memory erased. load mode records keystrokes overwriting memory locations. the back, step and goto keys can be used to reposition the step for overwriting. run mode is normal operation.

conditional and unconditional jumps are possible with skip jumping over the next instruction (key or goto xx) if the current value is negative (ie skip if neg). the manual describes some creative use of skip for other conditions. eg n1=0 is n1 x^2 +/- skip (n=0) (n!=0). pity there's no x^2 key.

the manual has a small program library which lists some weak offerings like; loan repayments that dont compute the repayment, herons triangle formula, areas of circles, segments, spheres and regular polygons. a bogus calculation of the length of an ellipse as sqrt(2(a^2+b^2)), volumes of cones, spheres and so on. all just simple formulae. a newton-raphson that requires you to code in both f(x) and its derivative, f'(x). inversion of a 2x2 matrix, and so on.

72 steps should be enough for a few interesting programs.
a slightly older version exists with a more boxy shape, otherwise the features are identical. the commodore name is printed on the foot instead of the head in this version.