What is Secure Digital card?
[[File:SDHC memory card - 8GB.jpeg|thumb|An SDHC card, with 8 GB capacity; this one is class 6. This means it has a minimum data rate of 6 MB/s]] A '''Secure Digital card''' (SD card) is a kind of memory card. Such cards are often used to store [[image]]s or [[data]] in [[digital camera]]s. As of 2008, different capacities between 4 [[Megabyte|megabytes]] and 32 [[Gigabyte|gigabytes]] have been made. The card has a [[Rectangle|rectangular]] design, but one edge is ''chipped off''. This means that the cards cannot be inserted into the cameras (or other devices) the wrong way. There are different kinds of cards: *Those labeled ''SD'', with capacities up to 2 [[Gigabyte|GB]] *Those labeled ''SDHC'', with capacities between 4GB and 32GB *Those labeled ''SDXC'', with capacities of up to 2 [[Terabyte|TB]] (the largest made is currently 1TB for SDXC or microSDXC). SD and SDHC are not compatible, but devices that accept SDHC also accept SD cards. The interface of SDHC and SDXC cards is the same, but SDXC uses a different [[file system]]. Some devices (for example the [[Wii]]) that originally shipped only with support for SD can be made to support SDHC with a [[firmware]] update. There are also different ''classes''. These refer to the read and write speeds. Currently in use are ''Class 2'' - which means 2 MBytes/second, ''Class 4'' - 4 MB/sec and ''Class 6'' at 6 MB/sec. The problem with this is that different manufacturers measure different things with it, some measure write speeds, others read speeds. There are also differences because some give guarantees, and others simply say that the speeds they indicate are the maximum achievable under good conditions. Still another measurement is called ''rating''. A rating of 1 corresponds to 150 KBytes per second, the read speed of a [[Compact disc|CD]]. That way, a class 2 is equal to a speed of 13x. [[microSD]] cards do the same thing but are much smaller. {{tech-stub}} [[Category:Computing]]