D2XX drivers allow direct access to the USB device through the FTD2XX.DLL. Application software can access the USB device through a series of DLL function calls. The D2XX APIs are categorized as Classic Interface, EEPROM Interface, Extended, and FT-Win32 APIs. Classic Interface APIs are standard calls to open the USB handle, close a USB handle, carry out read and write operations, and set UART features like baud rate and handshaking signals. EEPROM Interface APIs allow application software to read and program the various fields in the FT232R and FT245R internal EEPROMs or an external EEPROM used with the FT232B, FT245B, or FT2232D.