Secure Digital (SD) Cards – popular digital camera memory card format

Secure Digital (SD) is a memory card format used to transfer data between PCs and smaller devices, such as digital cameras, PDAs, MP3 players and mobile phones. Because the memory used is solid state, i.e. it remembers what’s been written to it when the power is removed, the information stays on the card when it’s unplugged. In order to get the data onto a PC, a card reader, either integrated into the PC or connected via a USB port, is required. Laptop users can also use an adapter that takes SD cards and fits into a PC Card slot. A consortium of Matsushita (aka Panasonic), Toshiba and SanDisk developed SD because they had been outflanked by Sony’s introduction of Memory Stick, their own proprietary card format, in 1998. This had two features that neither MultiMediaCard (MMC) nor CompactFlash, (CF) the other major player in memory cards at the time, possessed: a write-protect switch and integrated copyright protection. SD came onto the market in 1999 and was based, at least physically, on the MMC format. SD cards are slightly thicker but this allows the contacts to be recessed to protect them from damage. The other major physical change from the MMC design was an asymmetrical profile, which prevents SD cards from being inserted the wrong way round. The closeness of the two designs means that MMC cards can be used in SD slots, but not the other way round. Multi-function card readers are available with a slot than can accept SD cards as well as MMC, SmartMedia, Memory Stick and xD-Picture Card. One interesting and innovative adaptation is SD Plus,...

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