From QB64 Wiki
ERDEV$ is a string function that returns the name of the last device to declare an error.
- device$ = ERDEV$
- Currently NOT supported in QB64!
- It will contain the 8-byte character device name if the error was declared by a character device (such as a printer), while it will contain the 2-byte block name (A:, B:, etc.) if the device was not a character device.
- It is set when ERDEV is set, meaning that DOS has encountered a error that prevents it from continuing.