SD cards are the most popular flash memory cards available in the market. There is a lot of variety when it comes to SD cards. Firstly they come in three different sizes. These comprise of the standard-size SD cards, smaller mini SD cards, and the even smaller micro SD cards. The latter were invented in 2005 and are becoming increasingly popular on smartphones and tablets. Even though the larger cards don’t fit in smaller card slots, adapters are available to enable micro and mini cards to be accessed by any device that accepts the standard size card.
These cards also come in three capacity types known as SD, SDHC and SDXC. The SD card can store up to 2GB of data. SDHC (SD high capacity) cards can store around 4 to 32 GB, while SDXC (SD extended capacity) cards range from 32GB up to 64GB.
Not all SD devices can access all SD cards of the same physical design. While standard SD cards can be read by anything, SDHC cards should only be inserted into SDHC or SDXC devices. The SDXC cards must then only be used with the latest SDXC hardware. You may lose data or even damage the SDXC or SDHC card if you try to use it in a device that does not support it.
SD cards are currently also available in five speed classes. These are known as class 2, class 4, class 6, class 10, and UHS-1 (ultra high speed 1). Many manufacturers label cards with data transfer ratings are sometimes also included. However, in practical terms the speed class is what really matters.