Since FTDI devices enumerate as a custom class, they need specific drivers to be installed on the PC. In conjunction with the USB device ICs, FTDI provides a complete, royalty-free solution of device drivers at the application and bus layers. An RS232 serial port application can be used without modification and by just using the VCP driver. The VCP driver causes the USB device to appear as an additional COM port available to the PC. Application software can access the USB device in the same way as it would access a standard COM port. The VCP driver is used in conjunction with the FTDI D2XX bus driver.