The IBM 5100 Portable Computer is one of the first portable computers, introduced in September 1975, six years before the IBM Personal Computer, and eight before the first successful IBM compatible portable computer, the Compaq Portable. It was the evolution of a prototype called the SCAMP that was developed at the IBM Palo Alto Scientific Center in 1973. Whether considered evolutionary from SCAMP or revolutionary, it still needed to be plugged into an electric socket.

A portable computer is a computer designed to be easily moved from one place to another, as opposed to those designed to remain stationary at a single location such as desktops and workstations. These computers usually include a display and keyboard that are directly connected to the main case, all sharing a single power plug together, much like later desktop computers called all-in-ones (AIO) that integrate the system's internal components into the same case as the display. In modern usage, a portable computer usually refers to a very light and compact personal computer such as a laptop, subnotebook or handheld PC, while touchscreen-based handheld ("palmtop") devices such as tablet, phablet and smartphone are called mobile devices instead.