The first IBM PCs I was exposed to as a kid in the early/mid 1980's booted into BASIC if you didn't insert a disk into the 5.25" floppy drive. I think if you b

The first IBM PCs I was exposed to as a kid in the early/mid 1980's booted into BASIC if you didn't insert a disk into the 5.25" floppy drive. I think if you booted in this mode, BASIC had no access to the floppy drive at all so you couldn't save your work (or we kids didn't know how). Better to boot from a floppy, then after it finished booting, swap the floppy for another one to save the silly BASIC games we were writing. Later on, we saw models with two floppy drives, so you could leave the floppy containing DOS and BASIC in drive A: and save your work onto the disk in drive B: Eventually, PCs began to come with hard drives and these naturally became drive C: So if you've ever wondered why Windows typically refers to the hard drive containing the OS as drive C: it's because drives A: and B: were the floppy drives.