As satellite-based navigation systems take over tedious steering chores, multitasking farmers are adding computers to their tractor and combine cabs, allowing them to e-mail, text and surf their way across the field. While it’s possible to fit a full-size laptop computer into a crowded cab, sub-sized netbooks and tablet computers can be easier to handle. Smartphones are an even more popular alternative, but their small screens can be limiting.

Since coming on the market in 2007, netbooks (so-named because they were marketed primarily for accessing the Internet) have become more powerful and larger compared to early 7-in. models. While still slow by laptop computer standards, the latest netbooks pack more processing power and come with screen-size options ranging from the single to low double digits.

Tablet computers have existed in various forms for two decades or more, but Apple’s iPad touch-screen tablet is the first to take off in a big way commercially. In the first 80 days after the iPad’s April 2010 release, Apple boasted it had sold 3 million of the tablets.

One analyst estimates that iPad sales could reach 16 million in its first year, roughly double the netbook sales record in that category’s first 12 months. But Apple won’t have the market to itself for long. Additional tablets using Google’s Android and Microsoft’s Windows 7 operating systems are expected to be on the market by year’s end, or early 2011.

Netbooks are available from myriad manufacturers. Recent introductions featured here are from Asus, an early netbook innovator, and industry stalwart Hewlett Packard. Both are powered by 1.66-gigahertz (GHz) Intel Atom N450 processors typical of the latest generation of netbooks, and use the Windows 7 Starter operating system