Secure Digital Card is called a SD card. It is an Integrated circuit which is stored in a compact and rugged. They are designed to store data and to enable the transfer of data between devices. These cards capacities range up to 1 GB to 4 GB. It is 32mm long, 2.1mm thick and 24mm wide. More compact form than this one is also available. The transfer speed of a SD card is 12.5MB/s. SD 1.1 is expected to raise this to 50MB/s and these cards were originally introduced by Toshiba, Matsushita and San Disk. There are two versions of SD cards and they are micro SD and mini SD.
SD is anon-volatilememory cardformat for use in portable devices and it is widely used indigital cameras, digital camcorders,handheld computers,PDAs,GPS receivers, video games and mobile phones.
Most of the SD cards ship preformatted with the FAT or FAT 32 file system like other flash card technologies. 4 GB SD cards can be used with many systems by being formatted with FAT 16 file system. The larger cards than 4 GB SD cards can be formatted with FAT 32 file system. Most consumer products will expect MBR partitioning and FAT16/FAT32 file system. These cards are plainblock devicesand do not in any way imply any specific partition layout orfile system.Other partition schemes than MBRpartitioning and the FAT file systems can be used in these SD cards. Consumers cause confusion because all SD-cards have the same physical shape and form factor.