A PC is one that adheres to the original PC, the 8 bit 8085, later the 8086, hence the "X86" generation designation. There has been loads of computers based on just about every 8 bit to hit the market. The PC helped to advance the double sided floppy and eventually to the 1.4 MB diskettes as the cpu's gained more addressablity on RAM, floppies and hard drive. The scientific community jumped on the CO-Processor and soon it became an integral part. Upward compatablity was the goal and was driven by none other than Microsoft. The wrote the first DOS for the IBM PC and later re-wrote it to reflect hardware differences of different mfgrs. MS-DOS became more common and came bundled on the machine. With the third party market almost equal to the OEM, hardware options further the advances and clued the mfgrs to the next inclusions on their boards to eliminate the need for after-market parts and hardware. As the devices get smaller and more and more gets included in that package, the PC may remain as a backup to one of those all in one things when you drop it.