Another important file is the board.h file, which is found in a subfolder of the boards folder, and named after the board the designer is using; in this case, the Microchip SAM4S-EK. This is where the board designer assigns a logical name to each of the microcontroller I/O pins. The user can modify this file to reroute signals to different I/O pins. ASF drivers will use this file to direct signals to the appropriate I/O pin. When the user builds the circuit board at a later point, this is the file it is necessary to modify to properly describe the board.