IBM AT/370 Manual To Operations page 49

Formatting and Transferring
1
With the DOS prompt (A>) on the screen, type:
FORMAT C:/S
then press the Enter
(.,_.J)
key.
2
Press any key to begin formatting your C fixed
disk.
Note: Formatting takes several minutes.
When formatting is complete, proceed with "Copying"
on page 3-14.
AT/370
System
Setup 3-13