Lin545: "personal" as "for use by a single user" would also include kitchen food processors, oven, television, consoles and smartphones, which are not PC.
Don't forget about the second part of the term! We are talking about "computers" i.e. devices that enable humans to compute faster. Be it mathematical calculations, computer-aided design (CAD) or computational fluid dynamics (CFD), only computers are suited for the task. Computers are made to create, everything else with a chip -- to consume. Thus video game consoles and smartphones are not PCs and neither are coffee machines. Even industrial assembly robots and numerical controlled lathes are having "controllers", not computers.
Lin545: The thin-client/server vs thick(fat) client covers the rest, so its directly not related to "PC". But thin-client can never be a "personal computer" and is always a "managed computer" (like Sun or IBM infrastructures for example)
I never said industrial mainframes are "personal". But they are computers in their own right.
Lin545: ...yet having root and physical access to server would not attach "personal computer" sticker, because they mostly run closed Solaris or AIX).
"Open/Closed" has nothing to do with the matter.
Lin545: 2. "PC" is personal computer is sense that it belongs and does what user wants it to...
My work machine does not belong to me. It is a property of my employer. Yet, it is a PC with Linux (and only Linux) on board. And on my previous workplace we had one PC (normal Windows machine) for like 5 workers (and no own laptops/notebooks allowed) so we had to share our times. But those were also "personal", because only one person could work at a time! :-)
Lin545: ...but "IBM PC" is only a marketing brand. With CP/M or *DOS it was still personal as even ROM BIOS were not signed and flash-restricted.
Back at the time there were a lot of personal computers. Too many to count. "IBM PC" is a brand, yes. It is the IBMs attempt to enter personal computer market at the time. Before that IBM only produced mainframes so it is only natural that a computer produced by IBM and aimed at a single user at work would be called "IBM personal computer". ^_^
And "IBM PC/AT" was the last in the line of the IBM brand. Everything after that in legal sense can not be called "IBM PC". Thus the Intel 80286 processor with "PC DOS 3.0" or "OS/2" is the end point of "PC in a narrow sense". It is long gone past now.