This article originally appeared in the May 2011 issue of INTERNET TELEPHONY.

Both of the canonical graphical user interfaces were popularized by Steve Jobs (News - Alert), 23 years apart. That's quite an achievement.Applications that run in desktop PCs depend on a windowing GUI with a mouse.

These days it is hard to imagine a serious knowledge worker like an attorney or an accountant working at a desktop with less than two 20 inch screens. But the multi-window plus mouse user interface doesn't work on small screens, so on smartphones it has been replaced by page-able, scrollable, zoom-able full-screen apps with multi-touch control substituting for the mouse and keyboard.

These fundamental differences in GUI between mobile and desktop devices mean that application developers must write two completely different user interfaces for products they expect to run on both phones and desktops, even thin-client applications. The activities associated with these devices are also different.

Content creation (like writing documents, creating spreadsheets, editing presentations and movies) demands a desktop-type environment. Content consumption can be done on either type of GUI. Desktops can't do apps like camera, flashlight, navigation, magnifying glass or wallet, though this is more a function of mobility and form factor than GUI.This cut-and-dried distinction falls apart on intermediate devices. Laptops, tablets and netbooks are semi-mobile. (They all have Wi-Fi but, only some have WAN data).

Laptops and netbooks all have the window/keyboard/mouse interface, but their screens are too small to take full advantage of it. Some tablets have screens large enough to tempt content creation, but typing and even simple activities like cut and paste are awkward in a multi-touch environment.

Although Apple brought the window/mouse GUI to the mass market with the Mac, Microsoft (News - Alert) ended up with higher sales volumes. Similarly, while Apple brought the multi-touch GUI to the mass market with the iPhone, Google seems destined to sell more copies of Android, for the same reason: It is offering it to multiple hardware manufacturers.