Who develops and maintains the Secure Digital memory card standards?
Toshiba invented flash memory devices, and SanDisk created durable flash memory form factors, but it was the SD Association, formed by Toshiba, SanDisk and Panasonic, which developed the Secure Digital standards.
An SD card is a solid-state device. What does that mean?
Flash-memory technology allows computers and other electronic devices to save data without relying on a spinning disc, such as a hard drive, CD or DVD. Instead, it uses materials and circuitry to control an electric current and flip charged cells that represent each bit of data to be saved.
What sizes are SD cards available in?
The three sizes you'll see SD cards in are the standard SD (32 x 24 millimeters), miniSD (20 x 21.5 millimeters) and microSD (15 x 11 millimeters).
The terms SD, SDHC and SDXC refer to what SD card feature?
These three capacity formats (SD, SDHC and SDXC) are listed in order of development from oldest to newest, and in order of capacity from smallest to largest.
SDXC cards come in which sizes?
SDXC cards come in the standard SD size and microSD, but not miniSD.
True or False: In SD cards, the Speed Class standard and the UHS Speed Class standard are not compatible.
While the Speed Class standard applies to all SD cards, the UHS Speed Class applies only to cards that use the Ultra High Speed (UHS) bus interface, a data transfer technology within the card's circuitry.
True or False: SD card speed is an important factor in the quality of video recording and playback.
The faster an SD card's speed, the more data it can capture during recording and the smoother your video playback from the card. SD cards with the UHS Speed Class standard UHS-I can read and write up to 312 MB per second, which contributes to high-quality recording and playback.
True or False: The Media Identifier and Media Key Block (MKB) used to protect data by CPRM are saved to the SD card's FAT filesystem.
The Media Identifier and MKB are saved to a physical portion of the SD card's memory called the Protected Area. This area is not part of the SD card's accessible FAT file system and instead relies on technology within the SD card reader.
What technology is behind the secure part of Secure Digital cards?
CPRM is the SD card feature that allows a device to encrypt data so that any copies you make to different storage devices will be unreadable.
CPRM technology is part of the SD card standards. What does CPRM stand for?
Content Protection for Recordable Media (CPRM) was developed by 4C Entity, LLC, and it's now available in every SD card.
True or False: The write-protection lock on the side of an SD card permanently locks the file system, making it read-only and preventing any further changes to the data on the card.
The write-protection lock is a toggle switch between read-only and read-write capability. Lock the drive to prevent changes to files on the card, and unlock it again to remove, change or add data.
Which of the following is the smallest-sized SD card with the largest capacity?
SDXC cards have a larger capacity than SD and SDHC cards. Likewise, microSDXC, the smaller of the two extended capacity format cards, has a larger capacity than its microSD and microSDHC counterparts.
What is the maximum speed associated with Speed Class 2?
The lowest speed SD cards are those using the Speed Class standard with a classification of 2. Speed Classes 4, 6 and 10 all have a maximum speed of 25 MB per second, though each higher number does indicate a faster speed class than the previous.
True or False: A microSD card can be used in a larger SD card slot.
Provided the SD card reader can read the capacity format that matches the microSD card, you can slide the microSD card into an adapter designed to the larger-sized SD card reader. Some manufacturers sell microSD cards together with standard SD adapters for easier portability between devices.
What method does the SD Association recommend for formatting an SD card?
The SD Association recommends downloading and installing its SD Formatter software for formatting SD cards. While you could use disk management utilities like those for formatting hard drives, those utilities could damage the Protected Area of the SD card associated with its copy-protection technology.
According to flash memory creator Toshiba, how may write/erase cycles can the flash memory technology in an SD card reader go through in its lifetime?
Toshiba said an SD card can last 10,000 cycles, approximately the same as writing and erasing the entire card's contents once a day, every day for 27 years.
True or False: Any SD card that fits in the SD card reader of your device should be compatible with that device.
In order for a device to read and write to an SD card, it must be able to accept the capacity standard for that card. SD can be used in SDHC- and SDXC-capable devices, and SDHC can be used in SDXC-capable devices. However, newer-standard cards cannot be used in older-standard SD devices.
True or False: You can use an SD card reader to add a Bluetooth radio to your laptop computer.
Manufacturers have followed standards set by the SD Association to develop devices other than SD cards which rely on the power and input-output interface of the SD card reader.
What standard covers using an SD card reader slot for plugging in other kinds of devices, like wireless radios and TV tuners?
The SD Association realized the demand to use SD card slots as interfaces for devices other than the SD cards themselves, and they developed the SDIO standard to cover the input-output interface for such devices.
Which of these products uses the SDIO standard to add a Wi-Fi radio to your camera and the ability to upload photos directly to the Web?
Eye-Fi, Inc., has patents pending for its Eye-Fi card technology, which can connect to a Wi-Fi network and use that connection to upload photos to any of 25 Web sites, including Facebook and Flickr. The other two choices here are a Wi-Fi adapter (Socket Mobile Go Wi-Fi!) and a USB adapter (Mobidapter).
SD cards can sock away gigabytes of data like nobody's business. They're small and reliable, perfect for digital cameras, smartphones and other portable electronics. Test your knowledge of these flash-memory wonders.
About HowStuffWorks Play
How much do you know about dinosaurs? What is an octane rating? And how do you use a proper noun? Lucky for you, HowStuffWorks Play is here to help. Our award-winning website offers reliable, easy-to-understand explanations about how the world works. From fun quizzes that bring joy to your day, to compelling photography and fascinating lists, HowStuffWorks Play offers something for everyone. Sometimes we explain how stuff works, other times, we ask you, but we’re always exploring in the name of fun! Because learning is fun, so stick with us!
Get smarter every day! Subscribe & get 1 quiz every week.
Playing quizzes is free! We send trivia questions and personality tests every week to your inbox. By clicking "Sign Up" you are agreeing to our
and confirming that you are 13 years old or over.