Secure Digital High Capacity cards or SDHC are memory cards that are non volatile in nature. SDHC are so called for their very high capacities. Secure Digital cards with capacity greater than 4GB and going as high as 32GB are called Secure Digital High Capacity cards. The 32 GB SDHC card was launched in mid- 2009. An even higher version of this called the SDXC or Secure Digital Extended capacity card, has a capacity of up to 2 Terabytes. This particular product and the format have now become extremely popular. All of the Secure Digital (SD) cards possess the same dimensions and shape. This often confuses the consumer.
The Secure Digital High Capacity (SDHC) is basically an extension of the standard SD card. The only difference being a higher capacity of 32GB. SDHC cards have the same electrical and physical form factors as the older versions of SD cards (SD 1.x). This way the SDHC devices support both the older SD cards and the newer SDHC cards. The addressable storage in SDHC is increased by employing the sector addressing technique as opposite to the byte addressing format that was used in the older versions of SD cards. Sector addressing supports capacities up to 2TB.currently, the maximum limit of the SDHC card is 32 GB.
There are several compatibility issues between SD and SDHC cards. Generally it is seen that devices that do not support SDHC are unable to recognize SDHC cards unless they are incorporated with a firmware upgrade. SDHC cards are generally formatted as FAT32 file system in contrast to SD cards that have the FAT16 file system. Also, SDHC cards are compatible backwardly with the standard SD cards. The use of FAT32 file system cannot be averted since only this file system supports cards with capacities greater than 4GB.