“The impetus was the tablet,” said Nick Reynolds, Lenovo’s executive director for worldwide consumer products. “Unless the personal computer becomes interesting and personal again, it’s going to die.”

The explosion of these “multi-mode” laptop computers is the latest indicator of just how dramatically the computing industry has been turned upside down since Apple Inc.’s introduction of the first iPad almost three years ago.

Since then, sales of tablets have consistently exceeded even the most optimistic projections. Companies that were once leaders in selling personal computers and laptops, or the components such as chips and processors that go inside, were caught flat-footed by the turbocharged pace of change.

According to the Consumer Electronics Association, which hosts the Consumer Electronics Show, tablets and smart phones, two categories that barely existed a few years ago, will account for 40 percent of global sales of all consumer electronic devices in the coming year.

Some companies have scrambled to build their own tablets, usually based on Google Inc.’s Android operating system, with some limited success. Last year, Microsoft unveiled its own tablet, Surface, based on the new Windows 8 platform.

But many other companies are trying to reinvent the laptop.

Glimpses of some of these devices were seen at the last Consumer Electronics Show. But since the release of Windows 8 in October, a trickle has turned into a flood. By the end of 2013, chip maker Intel Corp., which is making big bets on these new devices, is estimating that there could be as many as 140 varieties of these multi-mode computers on the market.

These new forms offer consumers unprecedented choice. The risk is that they also create confusion.

For instance, a consumer might consider a convertible Toshiba Satellite. Open the top, and you have a laptop running Windows 8 with a touch screen. Open until both halves lie flat, then slide the screen over the keyboard to switch to a tablet.

Or check out Lenovo’s Yoga, which the company calls a “flip and fold” because its hinges allow a user to open the screen and place it in four positions: tablet, laptop, tent, or stand. The company also has the ThinkPad Twist, which opens and then lets the screen spin on an axle and close again so the screen faces up and hides the keyboard.

On Jan. 7, Asus announced its 13-inch Transformer Book, a laptop with a detachable touch screen that can be used as a tablet.

Acer didn’t unveil a new convertible at the Consumer Electronics Show, but its Iconia W510—released in November—is a tablet PC featuring Windows 8 and a sleek convertible design that can be used in three different modes to make computing more natural and intuitive: tablet, productivity, and presentation mode.

In productivity mode, a keyboard dock seamlessly connects to the tablet PC, transforming it into a full-featured notebook for a natural typing experience. The keyboard dock houses an additional battery, extending battery life up to 18 hours. Rotating the keyboard back 295 degrees allows it to be used as a hands-free stand for presentation mode.

Dell, meanwhile, introduced a convertible tablet, the Latitude 10, that it says is ideal for schools. The Latitude 10 is available with an optional productivity dock for desktop content creation activities. A full-size USB port provides connectivity to existing equipment, and an SD card reader enables easy file transfer and back-up when internet access is not available.

(Next page: The future of computing?)