Using Spooled Unit Record Devices

On the other hand, assume that instead of dedicated unit record devices, your virtual machine has spooled unit record devices. This means that your virtual machine does not have exclusive use of a real printer, punch, and card reader. As a result:

When you print or punch information, the information does not go directly to a real printer or punch. Rather, CP places the information into a spool file, which is on a DASD. When the spool file is closed (that is, CP is notified that the spool file contains all the information it is going to contain), and a real printer or punch is available, CP can print or punch the spool file.
When you read information queued for your spooled reader, what you are actually doing is reading a spool file that CP has placed on a DASD.

If your virtual machine has spooled unit record devices, you may need CP commands and the commands of the operating system you are running to manage the device. You need the commands of the operating system you are running to send information to your spooled printer or punch and to read information queued for your spooled reader. You need CP commands to manage your spooled unit record devices and spool files queued for your spooled unit record devices.