| ▲ | cyanydeez 2 hours ago |
| A: drive is 3.5; B: drive is 5.25; C: drive is hard disk |
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| ▲ | dspillett 2 hours ago | parent | next [-] |
| A: and B: were not specific to the type of drive. It was common to have two drives before fixed storage became common, often you would have the application disk in one and your data disk in the other though there were other common use patterns for two drives also (with the OS, or at least the core of it, resident in memory you can copy and otherwise manage data over two data disks, and so on). The first hard-drive in a system was made C: to reserve A: and B: in part because there was software out there that assumed A: and B: were floppy drives and could cause problems if something else was allocated to those signifiers. There are many things that are due to long forgotten compatibility issues like this (try naming file LPT1 under Windows to see another). Another reason is that the BIOS on many PCs was just hard-wired to assume two floppy drives so DOS would see that even if there were no drives really there. |
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| ▲ | cesarb 2 hours ago | parent | next [-] | | From what I recall from the time I still used MS-DOS, even if you only have one floppy disk drive, it's accessible as both A: and B: and it prompts you to insert the other floppy disk when you change the drive letter. That is, it's "virtualizing" two floppy disk drives using a single physical one. That explains why the first hard disk drive was always C: even when you only had one floppy disk drive (and of course you had at least one floppy disk drive, how could you use a computer without one?) | | |
| ▲ | Sharlin an hour ago | parent [-] | | Which is very convenient (and necessary for backwards compatibility) because programs could be (and were) written to assume they're in B: (and the DOS disk is in A:), or that they're in A: and the user's data is in B:, or a two-disk program is in both. All of that just worked (tm) even with a single drive, as long as the program didn't try to interleave accesses to both drives (I think it would still work because DOS was single-process, single-thread, it would just annoy the user!) |
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| ▲ | brewmarche 2 hours ago | parent | prev [-] | | I thought MS-DOS had special handling for A: and B: since it allowed you to copy from A: to B: even with just one floppy drive. | | |
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| ▲ | compiler-guy 2 hours ago | parent | prev | next [-] |
| Even further back into time, before 3.5" disks, both A: and B: were 5.25" disks. And, although my memory is hazy, 3.5's were commonly slotted into B: at first, because no one had 3.5" boot disks until the drives became somewhat common. |
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| ▲ | gumby 2 hours ago | parent | next [-] | | You are forgetting 8” floppies. IBM used only the soft sector ones (one hole punched close to the spindle to mark sector 0) but there were also hard sector ones (a ring of 32 holes close to the spindle hole). There was a lot of experimentation back in those days. The Wikipedia’s page on floppy disks is surprisingly long! | | |
| ▲ | LukeShu 23 minutes ago | parent | next [-] | | But those weren't on "IBM PC"-compatibles, just older micros? The 5150 had 5¼" drives. That is: (Q|MS|PC)-DOS never supported 8" floppies, right? | |
| ▲ | jasomill an hour ago | parent | prev | next [-] | | Floppies, superfloppies, removable hard disks (platter-only, as opposed to modern external hard drives that incorporate the entire drive mechanism), magneto-optical disks, rewritable CD/DVD, even today magnetic tape is still used as removable storage in applications where large capacity is required and shelf life is more important than fast random access. | |
| ▲ | compiler-guy an hour ago | parent | prev [-] | | Trust me, I will never forget 8" floppies. But in the context of drive lettering, although CP/M supported 8" floppies, MS-DOS never did. MS-DOS adopted the naming scheme, but not the boot style. |
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| ▲ | raldi an hour ago | parent | prev [-] | | The floppies got A and B because hard drives were expensive and for a time a lot of people got by without them, though everybody had at least one floppy. Even if you only had one floppy, it was both A and B, so you could say "copy a:DOC.TXT b:" and it would read the doc and then ask you to insert the floppy you're considering B (and depending on file size and available memory, sometimes switch back and forth a few more times) |
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| ▲ | alightsoul 2 hours ago | parent | prev [-] |
| Yeah it's a relic from when computers booted off floppy and hard disks were rare and expensive |
