This source code supports Microchip?s Application Note AN1045: Implementing File I/O Functions Using Microchip?s Memory Disk Drive File System Library, which describes the usage of file I/O functions using Microchip?s memory disk drive file system library. Microchip?s memory disk drive file system is:? Based on ISO/IEC 9293 specifications? Known as the FAT16 file system, used on earlier DOS operating systems by Microsoft? Also supports the FAT32 file system? Most popular file system with SD (Secure Digital) card, CF (CompactFlash®) card and USB thumb driveMost SD cards and MMCs (MultiMedia Cards), particularly those sized below 2 gigabytes (GBs), use the FAT16 standard. The FAT32 standard can be used to address memory sized between 2 gigabytes and 2 terabytes. This application note provides a method to read and/or write to these storage devices through a microcontroller. The data of these storage devices can be read by a PC, and the data written by a PC can be read by a microcontroller. Most operating systems (i.e., Windows XP) support the FAT16 and FAT32 file systems.