The Chordic Keyboard on a
  Multi-touch Sensitive Screen

This GKOS layout only requires one keypress per hand (1 + 1 fingers/thumbs):

GKOS For Thumbs
  Four extra bars have been added to enable simultaneous pressing of the top and bottom keys, as well as all three keys.
G, K, O and S keys have the same size of effective area as A to F and indicate pressing the two neighbouring keys.
Please note that there is no need to memorize any character tables because all symbols will appear on the keys.

Android, iPhone and Windows Phone 7 GKOS applications - More about design >>

The back-panel GKOS alphabet as a reference (3 + 3 fingers):
GKOS Alphabet
The character sets are exactly the same for both mehods. All PC keyboard functions and characters can be made available.
On the touch screen, you do not even need this cheat sheet!

GKOS for Thumbs application development information

Basic Guidelines for software and design
- Follow the character set to the least detail, else the whole idea of a harmonized keypad will be lost.
- Keep in mind that the effective areas of keys A to F and G, K, O and S should be of the same size.
- Pressing G, K, O and S really mean the same as pressing both neighbouring keys simultaneously.

The GKOS keyboard operation principle while using thumbs to type
This is the way different symbols and characters are shown on other keys while one key is pressed (shown in blue).

The figure on the left shows how the GKOS keyboard looks
like on the touch-screen when no keys are pressed.

The figures below show for each key pressed
how the characters on other keys change.

A pressed

D pressed

O pressed

G pressed

B pressed

E pressed

S pressed

K pressed

C pressed

F pressed

TH pressed

W pressed

Backspace pressed (The symbols on the right hand keys: Left Arrow, Word left, Home)

Space pressed (The symbols on the left hand keys: Right Arrow, Word right, End)

In 123 Mode or after pressing #@ (SYMB) the corresponding parallel set (123 set of SYMB set) is shown in a similar way. It is not necessary to implement the SYMB character set for providing all characters; it only speeds up typing single characters from the parallel set (123 or abc mode sets). The first iPhone GKOS keypad application does not have the SYMB option, just the abc, 123 and Shift sets, but still all characters can be typed. - The light blue color indicates areas that may also be highlighted to more clearly show that the smaller keys, hidden under thumbs, are pressed. This also helps associating the character to the form that the corresponding highlighted keys create (e.g. 'P' and 'J').

Here is the table of characters for implementing the application: http://gkos.com/table which also includes a link to native (national) layouts.

Created 12 March 2010, Blue highlighting edited 13 March 2010, The upper thwo pictures added 5 May 2010, Text editions 8-17 May 2010. Minor styling of images 31 May 2011.