If counted as notebook computers, iPads would have been the third largest seller in that category, ahead of Toshiba, Lenovo and Dell in the second quarter, after only two months on the market.

The tablet computer surge is leading to an increase in hiring -- in China. Foxconn International Holdings, which manufactures the iPod, iPhone, and iPad for Apple as well as other electronic gear for Dell, Sony and HP, among others, is planning in the coming year to add 400,000 manufacturing jobs to the 900,000 it has already. That will give Foxconn three times the number of employees as Apple and Microsoft combined.

The new units will offer increased functionality over the iPad as well as lower prices; the competition might even force Apple to reduce its prices. When competition heated up for the iPhone3, Apple cut prices by almost 50%.

The current iPad models range in price from $499 for a 16-gigabyte Wi-Fi-only system to $829 for a 96-gigabyte unit that can run on either Wi-Fi or 3G networks. It is powered by an Apple 1-gigahertz A4 processor and has a 9.5-inch screen. Note that Apple will also upgrade its tablet line by the end of the year.

RIM will announce its BlackPad tablet -- comparable to Apple’s $699 model -- by November at a price of $499. And Google will weigh in with a tablet that will go on sale Nov. 26 -- the day after Thanksgiving and the busiest retail day of the year.

The Google entrant will be built by HTC, a Taiwan-based company best known for its smartphones, and is based on NVidia’s Tegra 2 platform with a 1280-by-720 pixel multitouch display, 2 gigabytes of RAM and Wi-Fi/Bluetooth/33G connectivity. It will run the Google Chrome operating system. It will be marketed in conjunction with Verizon and will be substantially cheaper than the iPad.

Among functions not available on the iPad that will be offered on the new tablets:

• The addition of a USB port on the Windows-based tablet from Microsoft.
• Support for Adobe’s Flash software, which accounts for 90% of Web video.
• Crisper screens.
• Dual core processors for higher speeds.

Some of the units -- particularly one being developed by Verizon and Motorola -- will have the capability to stream live television to the screen. Verizon will also launch an app for the iPad this year that will let FiOS subscribers watch the same programming on that unit as they do on their TVs, but only when they’re home, for the present.

Almost all of the new units will have dual cameras -- one facing forward and one backward -- so a user can send pictures while videoconferencing.

Many of the new tablets will run on Google’s popular Android or Chrome operating systems. Android captured 33% of the smartphone market in the second quarter, ahead of both BlackBerry and iPhone. Others will run on Windows.

One intriguing feature being studied is dual touch screens: one on the front of the tablet and one on the back. Samsung has filed a patent for such a device, but it’s not clear how far along development on the unit, known as the Galaxy Tab, is. Apple is not standing still. It will offer a version of the iPad with a seven-inch screen this fall. That is the size of the screen used in e-readers such as the Kindle from Amazon and Nook from Barnes and Noble. Some users prefer the smaller size because it makes the device easier to lug around. An even smaller version is in the works that would really blur the line between smartphones and tablet computers.