Yashid - principle

Toke Eskildsen


Yashid stands for Yet Another Single Handed Input Device. Yashid is inspired by musical chords and is meant for mobile devices. Key-phrases are:

Physical use

Yashid requires a number of physical buttons in order to work. To uphold the ergonomic principle, the maximum number of buttons are 5 - one for each finger on a single hand. In practice 4 buttons for the entry and 1 separate button for mode-change and control (i.e. turning on text-input, switching letter-case and such) seems to be appropriate, since it maps neatly to using the thumb for the separate button and the rest of the fingers for the remaining 4 buttons.

Maintaining grip on the device while pressing the buttons isn't expected to be a problem, since the fingers doesn't move around, they just grip light or hard depending of the buttons to press.

Problem: For a right-handed person, the most natural use of such a device would be to hold it in the right hand and squeeze the appropriate buttons. That principle is hard to combine with a pen-using PDA, since the pen is normally held in the right hand. Such a combination would either require the user to operate the pen with the left hand (akward) or squeeze the buttons with the left hand (akward).

64 possible characters (in a single mode) combined with 4 lines for the reminder and at least one line for the entered text translates to a minimum display-capability of 5 lines, each with 16 characters.


In order to ease learning of the Yashid, the concept of a reminder is introduced. The reminder constantly displays the result of a potential action (i.e. pressing a button), thereby making it possible to use the device from day one.

Using 4 buttons for text-input, the reminder logically requires at least 4 lines on a display to provide appropriate feedback.

Entering text

The following principles underlies the algorithm for text-entering:


The layout for the characters is problematic. Alphabetic ordering makes it easy to scan and find a particular character, but is not very optimal. Statistic-based ordering is dependent of the kind of text to write, not to say language.


In the following example, a simple alphabet of the letters a-z, the numbers 0-9 and the special characters in the brackets [ ,.!?] are used. The ordering is alphabetic.

Legend with example:
Button Character Possibilities
1 e abcdfghijk

If the user pressed the button 1 and releases all buttons, the letter e is entered. The letter e is the most common letter from the letters a-k and is therefore the default.

If the user presses button 1 and holds the button, the user is presented with the possible ways of entering any of the letters abcdfghijk.

Entering the letter k

Upon entering text-entry-mode, the reminder displays all possibilities:
1 e abcdfghijk
2 r lmnopqstuv
3 y wxz0123456
4 7890,.!?

The user sees that the letter k is in the row corresponding to button 1. He presses and holds button 1. The reminder changes and reflects the new choises:
2 b acd e
3 f gh
4 i jk

The row for button 1 is no longer displayed, since we only allow each button to be pressed once. Instead the letter e is displayed to the right. If the user releases all buttons (that is: button 1), the letter e will be entered.

The user needs to enter the letter k, so he presses button 4:
2 j i
3 k

If the user releases all buttons, he will enter the letter i. He needs to enter k, so he presses button 3:

The only possibility now is to release all buttons. The user does that, which means the letter k is entered and the reminder returns to the starting position:
1 e abcdfghijk
2 r lmnopqstuv
3 y wxz0123456
4 7890,.!?

The complete sequence of presses for kilo could be: 143, 14, 213 and 23.

Toke Eskildsen, 27. march 2001