"Portable" personal computers have been around since before the IBM PC but the "Compaq Portable" (1983) - affectionately called a "luggable" - really started the revolution so many years ago. By the late 1980's, Toshiba was selling "laptops" which still required plug-in power.

By the 1990's battery-powered laptops were widely available but still quite expensive.

During the first decade of the new century notebooks had become the new standard in low-cost high-performance. Though the term "tablet" was associated with with high-end PCs for most of the decade - until the Apple iPad came along.

All that said, the tablet is really just the new "thin client" ... a portable device intended to deliver content from the clouds via this applications.