For input files

The device type you enter on the FILEDEF command indicates the device from which you want records read. It can be DISK, TERMINAL, READER (for input from real cards or virtual cards), or TAPn (for tape). Using the above example, if your input file is to be read from your virtual card reader, the FILEDEF command might be as follows:
filedef inputdd reader
Or, if you were reading from a tape attached to your virtual machine at virtual address 181 (TAP1):
filedef inputdd tap1