What was the first P.C.?

Identifying the first-ever "personal computer" is a tricky business. It depends on how one chooses to define a personal computer. Is it a computer designed for home use, or simply a computer intended for a single user? Must it fit on a desktop, or could it have been bigger? And should it be affordable, or could it represent a significant outlay of funds?

Given all of these competing criteria, it should be no surprise that there is no consensus among historians and technology experts on just which machine was the first "P.C." - or even in which decade the first P.C. appeared