IBM 5150 Manual To Operations page 135

4
This message appears:
Insert source diskette in drive A
Strike any key when ready
BEFORE YOU PRESS A KEY:
4A
Remove the diskette that is in the drive.
4B
Insert your original diskette into the drive.
4C
Now press a key.
S
You will see the "in use" light come on while the
original diskette is being read, and then this is
displayed:
Insert target diskette in drive A
Strike any key when ready
BEFORE TOUCHING A KEY:
SA
Remove your original diskette.
SB
Insert the back-up diskette.
SC
Now press a key to tell DOS the correct diskette
has been inserted.
DOS 3-61