IBM 5150

If You Have Two Drives
1 Make sure DOS is ready and A> is displayed.
2 Insert your DOS Diskette into drive A: if it is not already
there.
3 Insert the back-up diskette into drive B:.
4 Type this:
format b:
and press the Enter key.
5 You will see this message:
Insert new diskette for drive B:
and strike any key when ready.
6 Press a key, because the back-up diskette should already
be in drive
B: (step 3).
DOS 3-31