information efficient text enty using dasher

Terry Jeske terry.jeske at
Fri Jun 1 01:11:41 CEST 2007

I gotta say that I just tried the Dasher applet and after just a little bit
of practice was humming along. I am very excited that this may (will <g>) be
available on openMoko.

On 5/29/07, Chris Ball <cjb at> wrote:
> Hi,
> I'm one of the Dasher developers, and am also interested in hacking on
> OpenMoko.  So, getting Dasher going is fairly likely.
>    > This pretty much means that you have to stare at the display all
>    > the time when inputting text.
> Yes, this is the main difference between Dasher and T9.  However, the
> comments about needing a lot of screen resolution or CPU aren't so true
> -- we did Dasher on the iPaq seven years ago at full-speed and using
> 150x150 resolution, and it works great.  The reason we get away with
> not so much resolution is that you're only really ever being asked to
> choose between five or so probable letters at each turn, and it doesn't
> take much screen space to show those, and you can predict whereabouts
> you're headed by knowing the alphabetic order of which character comes
> next.
>    > Sure - in theory, dasher may approach arithmetic coding in terms of
>    > information input.
> (I'm not sure what you mean by "approach" -- Dasher *is* an arithmetic
> coder, and matches the information-theoretic efficiency of one in
> terms of bits/input to characters/output.)
>    > But unless you can do the coding in your head, you've got to stare
>    > at the screen, making it less useful for environments where you've
>    > got vibration, sunlight, walking down the street, or less likely
>    > for a phone, if you're blind.
> Yes, but the Neo doesn't have a keyboard, and doesn't have keys for T9
> that you can use without looking at the screen, so I don't think this
> is a useful criticism.  Dasher's very tolerant of vibration and mistakes,
> unlike T9 on a touchscreen -- it's much like driving a car, in that if
> you oversteer or understeer you just correct yourself later, because
> it's all about navigation and where you end up.  We can type easily over
> 20wpm on the iPaq with a touchscreen and stylus.
> Thanks!
> - Chris.
> --
> Chris Ball   <cjb at>
> One Laptop per Child
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