Secure Digital

Secure Digital (SD) is a non-volatile memory card format developed by the SD Card Association (SDA) for use in portable devices. The standard was introduced in August 1999 as an improvement over MultiMediaCards (MMC), and has become the de facto industry standard.

Secure Digital includes four card families available in three different form factors. The four families are the original Standard-Capacity (SDSC), the High-Capacity (SDHC), the eXtended-Capacity (SDXC), and the SDIO, which combines input/output functions with data storage. The three form factors are the original size, the mini size, and the micro size. Electrically passive adapters allow a smaller card to fit and function in a device built for a larger card.

There are many combinations of form factors and device families, although as of 2013, the prevailing formats are full- or micro-size SDHC and full or micro SDXC.

The SDA uses several trademarked logos to enforce compliance with its specifications and assure users of compatibility.

Memory card

A memory card or flash card is an electronic flash memory data storage device used for storing digital information. These are commonly used in portable electronic devices, such as digital cameras, mobile phones, laptop computers, tablets, MP3 players and video game consoles.

History

PC Cards (PCMCIA) were the first commercial memory card formats (type I cards) to come out, but are now mainly used in industrial applications and to connect I/O devices such as modems. Since 1994, a number of memory card formats smaller than the PC Card arrived, the first one was CompactFlash later SmartMedia and Miniature Card. The desire for smaller cards for cell-phones, PDAs, and compact digital cameras drove a trend that left the previous generation of "compact" cards looking big. In digital cameras SmartMedia and CompactFlash had been very successful. In 2001, SM alone captured 50% of the digital camera market and CF had captured the professional digital camera market. By 2005 however, SD/MMC had nearly taken over SmartMedia's spot, though not to the same level and with stiff competition coming from Memory Stick variants, as well CompactFlash. In industrial and embedded fields, even the venerable PC card (PCMCIA) memory cards still manage to maintain a niche, while in mobile phones and PDAs, the memory card market was highly fragmented until 2010 when micro-SD came to dominate new high-end phones and tablet computers.