When I first came to the USA, it quickly became apparent that there was no such thing as, ice cream. You had to specify what flavor, what combination of flavors, what kind of cone, what you wanted on top of it, and so on. This is all enshrined in the song I scream, You scream, We all scream for Ice Cream. Coming from England, I was not used to dealing with such a wide spectrum of choices for such a simple thing as ice cream. And England had the worst ice cream I had ever tasted, made from hydrogenated vegetable oils; margarine, basically. But it only took a few “experiments” to catch on to the more complex American approach.

Today, it’s becoming apparent that there is no such thing as a computer screen, anymore. It could be a PC screen, a portable gaming screen, a laptop, an iPod, or iPhone, etc. On the other hand, TV screens have been getting flatter and bigger, and when it comes to displaying media, the distinction between the function of a TV and the function of a computer is also rapidly blurring. Maybe these new classes of screen should have names like:

• i-screen: Sony PSP, iPhone type of interface
  
• u-screen: Utility screen for desktop computers and laptops
  
• v-screen: Video wall, jumbo TV, home-entertainment screen
  

The arrival of the i-screen doesn’t mean that desktop or laptop u-screens are going away. Rather they will likely coexist, at least for the foreseeable future. This newly emerging standard will not necessarily replace the other screen sizes, but rather supplement them. For example, it would not be physically feasible for me to write my next book on an i-screen, but a laptop u-screen works well and is probably the lower limit for that kind of interaction. Similarly, there is no logical reason why one couldn’t plug their i-screen device into a v-screen wall.


So, what constitutes an i-screen? The pedestrian characterization of a display is its diagonal length, but that’s an ambiguous metric because a 5″ screen could have sides of length 3.0″ by 4.0″ or 4.2″ by 2.8″, depending on whether it had an aspect ratio of 3:4 or 3:2, respectively. The standard TV screen aspect ratio is 4:3 (AR = 1.33), while for HDTV it’s 16:9 (AR = 1.78). The golden rectangle has an AR = 1.62. The following table summarizes the dimensions for some of the more common i-screen devices now on the market. Click to enlarge.


The meaning of Height and Width depends on the orientation of the device. For something like an iPod or Zune, the default orientation is determined by the position of the thumb-wheel. For an iPhone it’s more ambiguous because it can be used in either portrait or landscape orientation. The actual screen resolution is determined by the pixel density of the display technology.

In the table, where the H and W dimensions were not available (denoted by *), I used Pythagoras to calculate them from the diagonal length and the aspect ratio. Since those calculations are tedious, I wrote the following R function to do it for me:

aspdims<-function(diag, asprat) {
 if(mode(diag) != "numeric" || length(diag) != 1) 
  stop("Bad 'diag' arg") 
 if(mode(asprat) != "numeric" || length(asprat) != 2)
  stop("Bad 'asprat' arg")
 r<-uniroot(function(x) (asprat[1]*x)^2+(asprat[2]*x)^2-(diag)^2, 
                       c(0,5),tol=0.0001)
 scrn<-c(asprat[1]*r$root,asprat[2]*r$root)
 cat(sprintf("Scrn Dims: (%3.2f, %3.2f) in; (%3.2f, %3.2f) cmn", 
  scrn[1],scrn[2],scrn[1]*2.54,scrn[2]*2.54))
}

which can be applied as follows:

> aspdims(4,3) # Oops!
Error in aspdims(4, 3) : Bad 'asprat' arg
> aspdims(4.3,c(9,16)) # Sony PSP
Scrn Dims: (2.11, 3.75) in; (5.35, 9.52) cm
> aspdims(6,c(9,11)) # Kindle 2
Scrn Dims: (3.80, 4.64) in; (9.65, 11.80) cm
...

Along with the smaller i-screen dimensions, we have a completely new interface emerging; one that necessarily departs from the paradigms pioneered by Doug Engelbart and crew. The mouse is gone, and replaced by touch gesturing: pinches, swirls, ... that remind me of that Seinfeld episode about "the move". The role of the keyboard is still in question, partly because voice recognition is not yet ready for these devices.

If you had told me 20 years ago that people would happily tolerate interacting with these small i-screens, even to the point of watching movies on them, I would've said you were crazy. Now it's pretty clear that they represent an emerging class of display. In a previous blog post I stated:

Mobile devices like this (iPhone) are actually computers, not just phones. The iPhone runs Mac OS X; same as mac laptops. In my view, this and similar devices represent the commodity computer of the future.

And the growing ubiquity of these i-screens is going to put a lot more pressure on Web 2.0 availability and performance, which brings us back to capacity planning, as usual.

Afterthought. Maybe the test for an i-screen is:

Can you put it in your pocket?

Kindle-2 would fail on this score, but only because of its keyboard.