Subtypes of laptop computers include many different types. UMPCs, or Ultramobile PCs. These small screen models are scaled down versions of larger portables and are designed with a miniature keyboard and mouse interface. Laptops containing screen that are typically smaller than 12 inches are considered ultraportables, and are primarily designed for business travelers who need small, light laptops. Other categories include thin and lights which weigh between four to six pounds, mainstream laptops, which weigh five to seven pounds, and desktop replacement computers, which are designed to remain in a fixed location and, as their name implies, are intended to replace traditional desktop computers in the workplace.

Similar devices are also available. The prototype for all laptops and portable computers, the Osborne 1, was intended to run desktop software but did not function well as a portable computer unless it was directly plugged into a power source. There are tablet devices shaped like notebooks that include touch screen interfaces and a magnetized stylus. Some do not include a keyboard, while others have convertibles that include a screen which can be rotated 180 degrees and folded on top of the computer. Personal Digital Assistants, or PDAs, also fall into this category, as well as smart phones, like the recent Apple IPhone.

The lines that separate these types of devices are often blurred. The Apple eMate, for example, had a clamshell form of a laptop, but ran PDA software. The HP Omnibook line also included some devices that were small enough to be classified as handheld computers.

The first laptop model proposed was Alan Kays Dynabook concept, which was developed at Xerox PARC in the early 1970s. The first portable computer to be made commercially available, however, as previously stated, was the Osborne 1, which was releaaed in 1981 and ran on the CP/M operating system. Although it was bulky by the standards of today, it revolutionized the business world, since business travelers were, for the first time, able to take their computers along on trips with them. The first portable computer, the Xerox NoteTaker, had already been developed by this time, but only a limited amount of prototypes were ever built, and although the Osborne was comparatively expensive and the size and weight of a portable sewing machine, it was nevertheless very popular in its day.