SDHC
full spelling ： Secure Digital High-Capacity
SDHC cards are top standard SD memory cards, announced by the SD Card Association (SCA) in January of 2006, that are designed to store 4GB or greater memory.
The SDHC format is innovative in that it guarantees a minimum data transmission speed (DTS). As such, "Class 2" SDHC cards guarantee a minimum DTS of 2MB/s, while "Class 4" and "Class 6" guarantee minimum DTS's of 4MB/s and 6MB/s, respectively.
Together with increased memory capacity, SDHC 2.00 specifications include a shift from FAT16 to FAT32, meaning that machines manufactured before the advent of SDHC 2.00 cannot read SDHC media. However, SDHC-compliant machines come equipped to read last generation SD memory cards as well. Note that while some (last generation) SD memory cards had a memory capacity in excess of 4GB, they were not compliant with the standard, which called for a maximum memory capacity of 4GB.
SDHC card's graphic resolution is improving year by year, and are expected to be used in digital cameras with larger screens, as well as digital video recorders, which place a premium on high-speed data recording.