A Clock (Modular) Arithmetic Calculator

If you don't have a java-enabled browser, you won't be able to see this applet.

Instructions

1. Choose the operation you want (+, -, or x) by holding down the button with the pull-down menu, and releasing on the one you want.
2. Type the first number you want to calculate with in the first box.
3. Type the second number you want to calculate with in the second box.
4. Type the number of hours on the clock you want to use in the third box (after "mod").
5. Click the "=" button to get the smallest nonnegative "name" for the result of the operation on the clock.

Problems? Got an "E"?

• Problems? Got an "E"?
  • All numbers must be whole numbers. Except for the modulus, they can be positive, negative, or 0.
  • The number of hours on the clock (modulus) must be a whole number at least 2.
  • If you type in a number bigger than the box, it will turn to an "E" (for Error) because this computer program can't handle numbers above a certain size.
  • You have to click "=" or hit the return key after typing for the program to calculate anything.

  Technical mathematical comments

  • The notation is not quite standard; the "mod m" part should come at the end of the sentence, not in the middle. And you should use the congruent symbol (3 horizontal bars) instead of the = sign.
  • Division is often impossible in modular arithmetic; check back here soon for an online calculator for dividing.
  • There will also be a calculator for exponents (raising to a power).

  Technical computer comments

  • This program uses the built-in java mod (%) operator. Because of limitations on the size of integers in java, this applet can't handle very big numbers. Maybe someday I'll fix it to deal with very long integers.
  • The source code.

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  Comments welcome: susan@math.csusb.edu

  To:
  Susan Addington's Home Page
  The Number Bracelets Page (a game to play with modular arithmetic)
  CSUSB Math Dept. Home Page ml>