SDHC (Secure Digital High Capacity, SD 2.0) is an extension of the SD standard which increases card s storage capacity up to 32 GB. SDHC cards share the same physical and electrical form factor as older (SD 1.x) cards, allowing SDHC-devices to support both newer SDHC cards and older SD-cards. To increase addressable storage, SDHC uses sector addressing instead of byte addressing in the previous SD standard. Byte addressing supported card capacities up to 2GB, whereas sector addressing can theoretically support capacities up to 2 TB (2048 GB). The current standard limits the maximum capacity of an SDHC card to 32 GB.canonglossaryus
A non-volatile memory card format for use in portable devices (Developed by Matsushita, SanDisk, and Toshiba.)
A further extension of the SD standard, the Secure Digital Extended Capacity (SDXC) format was unveiled in 2009, with a maximum capacity of 2 TB (2048 GB). The initial maximum transfer rate was 104 MByte/s, but that is expected to increase to 300 MByte/s. Microsoft s proprietary exFAT file system is the standard for this memory card format, but it is possible to use another file system, i.e. FAT32, NTFS or ext2.