In August of 1981, the IBM `personal computer' was launched. At an astoundingly low price, compared to mainframe and minicomputers, the PC offered computing power, inexpensive and convenient floppy disks for bulk storage, a monitor and keyboard for interactive use, printers and peripherals. What it didn't offer was any of the complex and resource-consuming trust management mechanisms of the time-sharing systems. Gone were the user ids, gone the passwords, gone the protected memory, gone the distinction between user and supervisor modes of operation. ``This is not a time-sharing machine!'' we can imagine somebody arguing, ``This is a computer for one person! Who's to protect from?"
And then of course, the PC had scarcely hit the market when the first PC computer viruses appeared and began to spread via those same convenient floppy disks, without the least bit of immunological defense by the PC.