5 Documentation

jeremysrand edited this page 2012-07-28 21:38:53 -07:00

Table of Contents

• Curta Simulator Documentation
• Controlling The Calculator
• Performing Calculations

Curta Simulator Documentation

There are two main things to know in order to use this Curta simulator for the Apple ][. First, what are the controls on the Apple ][ to manipulate the simulated Curta. Second, how to do you actually use a Curta calculator.

Controlling The Calculator

The calculator is controlled by a joystick. All operations on the calculator are done through a joystick "gesture" which means that you need to make at least two motions on the joystick for the calculator to recognize an action. All gestures start with the joystick centered. The simplest gestures involve moving the joystick to a position (perhaps to the left for example) and then returning the joystick to the center. Optionally, you may need to press and hold one of the two joystick buttons while performing your gesture.

When you launch the simulator, the screen has an 11 digit number on the top of the screen which defaults to all zeroes. Below the zeroes are a set of sliders which you can use to adjust the 11 digit number. By default, the right-most digit is selected and if you push down and then center your joystick, the right-most digit will increase in value. If you push up and then center your joystick, the right-most digit will decrease in value. As you do this, a slider will move down or up. That slider is a graphical representation of the number and corresponds to the sliders on a real Curta calculator.

You can push the joystick to the left or right and then center it to move the selected digit to the left or right. Note that on a non-colour screen, the slider drawn in black is selected. On a colour screen, the background of the slider will change as it is selected as well as the colour of the slider itself. These operations will allow you to enter any number you want.

At the bottom of the screen is a counter and result number as well as a carat which points to the right-most digit of the result. This is the output of the calculator. The carat controls the carriage position and determines which digits you are working with (one's, ten's, hundred's, etc). You can move the carat by holding down the first joystick button and pushing to the left or right and then centering your joystick.

There are three basic operations you can perform on the calculator. Each of them is performed by "cranking" your joystick. On a real Curta calculator, these operations are performed by cranking the calculator so the joystick is used to simulate that. A crank is performed by starting from the center, pushing down on the joystick and then proceeding around in a clockwise direction until you return the to down position and then back to the center. If you have troubles getting the simulator to recognize your "crank" gesture, try performing the crank gesture more slowly or re-calibrate your joystick to make sure you are getting a good center and range on in all directions.

The three operations are:

1. Add - Just do a crank operation with no buttons pressed. The number you have entered is multiplied by the carriage position (one's, ten's, etc) and then added to the result. The counter is increased by one at the carriage position.
2. Subtract - Just do a crank operation with the first button pressed. The number you have entered is multiplied by the carriage position (one's, ten's, etc) and then subtracted from the result. The counter is decreased by one at the carriage position.
3. Clear - Just do a crank operation with the second button pressed. The result and counter are reset back to zero. The carriage position is unaffected.

Performing Calculations

The best way to demonstrate how to use the calculator, we will go through an example. We will calculate "123 x 92". The first step is to set the number at the top to 123. Assuming you have just started the simulator and have no number entered, yet the following gestures should do this (where a gesture is a motion in the direction indicated and then back to the center):

1. Gesture down three times to set the 1's column to 3.
2. Gesture left to move to the 10's column.
3. Gesture down two times to set the 10's column to 2.
4. Gesture left to move to the 100's column.
5. Gesture down one time to set the 100's column to 1.

You should now have the number 123 in the upper part of the screen. Now we need to do the multiplication by 92. The gestures to do this efficiently are:

1. Crank twice. By cranking twice, you multiply 123 by two. The Counter should now say "2" and the Result should be "246".
2. Press the first button down and gesture left twice to move the carriage position to the 100's. The carat should now be pointing at the 2 in "246".
3. Crank once. By cranking once, you have added 100 * 123 to the result. This effectively means you have calculated "123 * 102". In fact, the Counter says "102" now and the result is in fact the result of that calculation which is "12546". But this is larger than the "92" we wanted to multiply by. It is larger by 10.
4. Press the first button down and gesture right once to move the carriage position to the 10's. The carat should now be pointing at the 4 in "12546".
5. Press the first button down and crank once. By cranking once with the button down, you have subtracted 10 * 123 from the result. This means you have calculated "123 * 92" which is what we wanted to calculate. The Counter is "92" and the Result is the correct answer which is "11316".

At this point, you can clear your work so far by pressing the second button down and cranking the joystick. And that is a complete calculation. You can search the web and find more hints on using a Curta. There are explanations on how to do basic add, subtract, multiply and divide operations out there. Have fun.