Opinions have changed since 2000, however, and today thousands of seventh graders in Maine have received laptops -- in part because Papert pointed out that the cost of the laptops was far less than the outlay for hiring enough teachers to significantly reduce class sizes. He also suggested the laptops could help reduce teachers' workloads, allowing students to work independently or more easily seek help from peers.

Others have suggested that laptops are luxury items, especially in countries where children lack food and health care. Papert responds that education is necessary for the long-term development to address these needs.

Shiva Mirhosseini is the leader of the Boston chapter of Shabeh Jomeh, an organization of Iranian professionals that, among other activities, purchases computers and other educational resources for needy children in Iran. She says the $100 Laptop could "nourish and empower a group of people who could make a big difference in the long term."

Still other critics have suggested an alternative: distributing refurbished desktops or cheap smartphones instead of new laptops. Neither of these options is preferable, however, in the view of Negroponte and Papert, since desktops are costly and nonportable and smart phones are difficult to type on. The two researchers argue that, far from being costly luxury items that become obsolete in months, computers can be inexpensive, durable tools. (Papert points to the digital watch he has been wearing for ten years.)

All of this depends, of course, on getting the cost of the first version of the device down to $100, and lower in the next generation.

"One hundred dollars, though that sounds impossible, is still far too expensive," Negroponte said in his address.

The group has built working trial versions of the device. Jacobson says the keys to an inexpensive, yet still useful laptop are an inexpensive screen and a lean operating system that can work with a slower, cheaper processor and less memory.

R&D continues on the operating system and the group has not made a final decision about the screen, although the LCD used in inexpensive portable DVD players is a strong candidate. Marketing and distribution costs will also be saved by selling in bulk to governments.

Maintenance and Internet connections aren't counted in the $100 price tag. To address those costs, the designers have considered making the parts easy enough for a child to replace, and they're giving the devices mesh-networking capabilities (see "Mesh Networking Matters") using Wi-Fi, which will allow them to connect to other nearby laptops or to a central computer for Internet access. The speed and number of these connections will vary according to the capabilities of local schools. 

Durability is another issue. Since kids will be using these computers, they've been designed to survive drops and to be water- and dust-resistant. (Papert, however, believes that if kids value the computers, they'll take care of them.)

Theft is one more concern. That issue is addressed, in part, by the distinctive design -- so that a stolen laptop would be obvious. But "if our real goal is to get these to as many needy people as possible," Jacobson says jokingly, "actually theft is a great distribution channel."

The $100 Laptop project "is the most important thing I've ever done in my life," Negroponte told the conference audience. Children connected via their laptops to the global Internet, he and Papert believe, will develop the knowledge and ambition needed to make their countries more effective competitors in global markets.

"Only part of learning comes from teaching," Negroponte said. "A lot of learning comes from exploration."