Note: There was a problem with one of the images (nodiamond) which caused the abacus to malfunction (I bet the Chinese didn't have this problem way back when it was invented); it should be OK now.

Magic is fun, but it's always

- overflow indicated by changing the display-color of the value to red and
prefixing the value with an "*"
*(Aug 1, 1995)*;

The classic abacus has two decks. Each deck, separated by a beam, has
several (normally 13) rods on which are mounted beads. Each rod on the
top deck contains 2 beads, and each rod on the bottom deck contains 5
beads. Each bead on the upper deck has a value of five, while each
bead on the lower deck has value of one. Beads are considered
*counted*, when moved *towards* the beam that separates
the two decks.

**FIGURE 2:***Numeric representation of the number: 87,654,321*

Similarily, the second column representing the number 7, is composed
of 1 bead from the top-column (value 5) and 2 beads from the
bottom-column (*each* with a value of 1, totaling 2); the sum
of the column (5+2) is 7.

When a sum greater than 10 occurs on a certain rod, beads are removed from either or both the upper and lower decks and 1 bead is added to the rod directly to the left. Example: When adding 9 (10-1) to 8, one bead from the lower deck is removed (-1) and one bead from the lower deck on the row directly to the left is added (+10).

Example: When subtracting 4 (+1-5 = -4) from 7 (represented by 1 bead in the upper-deck and 2 beads in the lower deck (less than 4, the subtracter), one bead is added to the lower deck (+1) and 1 bead is removed from the upper-deck (-5) leaving 3 beads, representing the result.

If you've actually read this user's guide up to this point, hoping to learn how to use the abacus to its maximum potential, I should tell you that you'd be better off using a hand-held (or pop-up) digital calculator. (I hear you asking: Why did I bother going through all this if I was going to expound this heresy at the conclusion? Essentially, the exercise was designed to be didactic; from my programming stand-point, it was an interesting program to attempt and hopefully, the user would learn a thing or two (admit it, you now know how an abacus works). Unquestionably, though, it was unmitigated fun!).

Technically, the abacus is a hand-held digital calculator, but that the user must perform some sort of arithmetic manipulations before the solution is arrived at.

A great debt of gratitude goes to Agustine Lee, instructor at the
Ryerson Electrical and
Computer Engineering Department, who supplied a real, live abacus
without which xabacus would not be possible, for supplying invaluable
documentation, that was shamelessly plagiarized into the documentation
you are now reading, for the Chinese characters, and for testing
`xabacus` and providing helpful comments on improving
it....

...thanks also to Nick Colonello, former sysadmin at EE and all-round technical-support person, for beta testing....

...and to Eva Dudova, who has expertise in unmercifully crashing applications (has a future as a beta-tester), and is cute too...

... and finally, thanks to those who have written X-applications and the demo Java applets, from whose code I have learned the art of X and Java.

The beads for the abacus, were generated using the Interactive WWW graphics generator. Check it out!

The Abacus: The Art of Calculating with Beads/ Luis Fernandes elf@ee.ryerson.ca