Numeric Calculator


A numeric calculator with basic functionality and a large easy to read numeric display. The keys can be themed with 10 different accent colors and the background can be either white or black. It can be used in portrait or landscape mode. An undo key is included which can be used to undo an operation or a clear key press.


Basic Calculator Landscape Left

The calculator uses a unique snap-action preview character as a visual indication that a key is pressed. When a key is pressed the key character is displayed in red on the right side of the active input window. When the key is released the character snaps into place in the active input window. If the character displayed is not the intended key, move your finger to the desired key until its character is displayed and then release, or move off of the keyboard and release to cancel the key press.


Operating Instructions


To provide quick access to settings and the help screen the app is set up as one continuous page in landscape mode as shown in the figure below. The virtual scroll wheel (2) will appear in landscape mode indicating that other features can be accessed by sliding your finger up or down along it. The scroll wheel will always appear on the side opposite the phone status bar.


Calculator details with baloon references
  • 1. Background color select menu
  • 2. Virtual scroll wheel
  • 3. Accent color select menu
  • 4. Numeric display window
  • 5. Keyboard
  • 6. Help Screen

When a key is pressed a preview character representing the key pressed will show up in red on the right side of the active input window. If the preview character is not the intended key, slide your finger to the desired key and then release your finger. To cancel any key press slide you finger off the keyboard until the preview character is no longer visible and release. If the key pressed is a numeric value (0 - 9) it will snap into place in the active input window when the key is released. If it is an operator that requires a second value,(such as the + key) the operator will be displayed until the next value is started. To change the operation press a different operator key and the preview character will change to the new operator. Or to cancel an operation press the backspace key. If the key pressed is an operator that does not require a second value (such as +/- key) the preview character will only be visible while the key is being pressed. Once the key is released the operation will be performed.


To perform an operation; enter a value, press an operator key, enter a value and press the equal (=) key. The result will be displayed after the equal key is released. For example enter 4 + 3 = and when the equal key is released 7 will be displayed. A running operation can also be performed by pressing an operator key in place of the equal key. For example enter 4 + 3 + when the plus key is released 7 + will be displayed indicating that the next value entered will be added to 7. A running operation can also contain mixed operators. Consider the following key sequence: 7 + 3 * 2 / 5 = when the equal key is released 4 will be displayed. The operations are performed in the order they are entered; first 3 is added to 7 and the result is 10; then 10 is multiplied by 2 and the result is 20; finally 20 is divided by 5 and the result is 4.


An undo (UNDO) key is provided to undo an operation or a clear key press. An operation which operates on two values (such as +) is added to the undo buffer when the operation is performed. For example if 4 + 3 = is pressed 7 will be displayed. Pressing the undo key changes the value back to 4. When the clear key is pressed, the value in the numeric display is added to the undo buffer before the clear operation is performed. If the undo key is pressed after a clear key press, the numeric display will be restored to its previous value. The undo key can restore up to the last ten operations and/or clear key presses.


When the value in the numeric display becomes too large for the display window, the font size will be reduced. For calculations with long numeric strings use landscape mode, since the larger display window can display more digits before the font size is reduced.


To change the accent or background color, switch the orientation to landscape mode. Then slide your finger down along the virtual scroll wheel to pull the background and accent color menus into view. Press and release on the desired setting. The new setting will take effect when the press is released. The settings are saved on the device so that the next time the application is started the new settings will be used.


The help screen can be viewed from landscape mode by sliding your finger up along the virtual scroll wheel. The key functions are described and any notes for the application can be viewed here. At the bottom of the help screen the calculator version and support information is shown.