![]() ![]() This is a list of different floppy disk formats. Some later ROM replacements like the excellent JiffyDOS system repurposed the tape code in their ROMs to provide a built in fast loader and DOS wedge (a whole other rabbit hole).8-inch, 5 + 1⁄ 4-inch, and 3 + 1⁄ 2-inch floppy disks The computers actually had a significant amount of precious ROM space dedicated to tape drive operation which was completely wasted in the later C64 timeline when most users were using disks exclusively. The disks were an add on later once disk drives caught on as the home computer medium of choice. Tape drives came first and were designed along side the computer architecture starting with the PET. While the disk drives were smart, the tape drives were dumb. A common blunder was to list the directory before saving and losing your work. That's why displaying the disk directory on a Commodore computer would clobber any BASIC program in RAM. The computers had no concept of a filesystem at all: displaying the disk directory involved a hack where the drive would construct a fake BASIC program and stream it to the computer when a special filename "$" was loaded. Commodore computers only understood a simple serial protocol and DOS commands like rename, delete or format disk were just sent as text commands on the serial command channel, which were interpreted and run by drive itself. Commodore had bought out MOS by this point and manufactured 6502 chips themselves, so the drive CPU was "free" in a sense.Īlso it's worth noting that the Commodore DOS talked about in the article was implemented and ran entirely on the drive, not the host computer.
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