My printer is a USB device. OPEN (UNIT = 4 FILE = 'PRN') and writing to 4 produces Severe Error (564). FILE = 'CON' does write to the screen. USB is not listed in the Physical Devices section of Help Files.
You can't write directly to a USB-connected printer. Opening PRN is a DOS technique no longer valid. Instead, you need to use Windows printing mechanisms. See Fortran_WinPrint.f90 for code you can use in your application to print a file.
