A new kind of device may be defined as much by what it leaves out as by what it adds.

The New York Times reported that Steve Jobs introduced the iPad tablet computer on Wednesday in San Francisco. The device is a tablet PC. Apple said the iPad is 0.5 inches thick and weighs 1.5 pounds, calling it thinner and lighter than any laptop or netbook. The company stated the hardware will be available in late March starting at a price of $499. The New York Times noted the device costs $499 to $829.

What the Device Shows, and What It Lacks

The device will vividly display books, newspapers, Web sites and videos. However, technology enthusiasts were quick to point out that the iPad lacks some features common in laptops and phones.

The reports do not say why those features are missing, and no reason is assumed here. In general, a device that does fewer things might ask people to use it differently.

Building Software Ecosystems Before Hardware Availability

Apple's press release said it had released a new Software Development Kit (SDK) for iPad so developers could create "amazing new applications" designed to take advantage of iPad's capabilities.

Offering software tools before the hardware goes on sale may suggest how much a new kind of device could depend on other people's software. Without apps made for it, a tablet might find it harder to earn a place between a phone and a laptop.

Perhaps a new device is judged as much by what others build for it as by what it includes.

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