Most common calculators in the forum?

[jlind]

(08-26-2019 11:42 PM)rprosperi Wrote:  

(08-26-2019 10:33 PM)jlind Wrote:  Other:
Magic-Brain (circa 1960)

Do tell and do show, please. Perhaps one of the mechanical slider type adding machines?

You made excellent guess :-D
Photo of one in a museum . . . mine is in better condition without the scratches. It's similar to a glorified abacus in how it operates. One carries a digit over to the next column (or takes one away in subtraction) by hooking into the next column's slider at the top or bottom. Whether you move up or down in the current column depends on (a) adding or subtracting, and (b) whether or not it's going to add a digit or subtract one from the next column. If adding "4" to the value shown in the photo (disregarding the decimal point), you would slide that column upward as there's not enough increments left for all "4", and then at the top, move to the left and increment the next column by one. That resets the current column to zero and since the next column cannot move, you have to manually carry the one over, which sets that column to zero and increments the next one when you hook around at the top. You can tell whether to move up or down by the color next to the digit you're adding or subtracting. Takes a bit of practice. The wire "handle" at the top, clears the machine by resetting all the columns to zero. Black numbers on sliver are for addition (or multiplication) and silver numbers on black are for subtraction. If you mentally follow an operation slowly you can see how it works. Moving a slider down increases the number shown. Moving it up decreases it. If white is showing on the slider next to the number you're adding or subtracting, you move up. If red is showing, you move down.



John