For UNIX and Linux Systems:
%> uname -n
mycomputername

For Windows systems:
C:\>hostname
MyComputerName

On Windows, this can also be found from the System Information Control Panel under the “System Name” field.

For Mainframe CPU information:
D M=CPU
The 4 digit CPU Serial number required to register is the last 4 digits of the CPC SI field - example:
CPC SI = 2964.732.IBM.84.000000000001AB12