A handheld PC is a miniature computer typically built around a clamshell form factor and is significantly smaller than any standard laptop computer, but based on the same principles. It is sometimes referred to as a palmtop computer, not to be confused with Palmtop PC which was a name used mainly by Hewlett-Packard. The name Handheld PC was used by Microsoft from 1996 until the early 2000s to describe a category of small computers having keyboards and running the Windows CE operating system.