Hardware Reference
In-Depth Information
heads must wait for the disk to rotate to the right position to do so. Hard drives
function in the same way, only the motor is included inside the drive.
Both l oppies and hard drives are susceptible to damage; for example, a hard
drive falling from your pocket might destroy the device. Flash memory works
differently. Unlike l oppies and hard drives, l ash memory has no moving parts,
and is therefore much more resilient to shocks and impacts. It requires very
little energy to function, and some forms of l ash memory have read and write
speeds far greater than the fastest hard drive available.
USB l ash drives still aren't the answer to our needs. We can now easily
transfer data from one computer to another, but mobile devices are becoming
more and more present. Mobile telephones, digital cameras, camcorders, and
mp3 players all require storage. Early devices had a i xed amount of storage,
and although it might have been more than enough for some, for others the
storage wasn't close to being enough. My i rst digital camera had 16 megabytes
of memory, more than enough for a quick photo shoot, but not enough for my
holidays. Users wanted choice, so companies turned back to a format that had
existed for as long as USB itself. Multiple mobile memory storage devices were
created, but the most dominant format is the SD card.
SD Cards
SD, short for Secure Digital, is an evolution over the previous MultiMediaCard
standard. The SD Card Association manages the format, specii cations, and evo-
lutions, and uses a trademarked logo to enforce compatibility. If your device has
the same logo as the one on your SD card, you know that they will be compatible.
Physically, SD cards are available in three formats: standard size, mini, and
micro (see Figure 12-3). Today, most devices use either the standard size format
(for larger devices, like cameras, camcorders, and personal computers) or the
micro-size format (for smaller devices, such as e-book readers, telephones, and
mp3 players).
SD cards are not only used for data storage, but also for data transfer. You
can transfer photos from your camera either with a USB cable or directly by
taking out the card and connecting it to your PC. Some desktop computers have
an SD-card reader, as do many laptops. For micro-SD cards, you have several
choices. There are USB readers that can read several types of cards or USB
keys that can accept a micro-SD card and be used as a regular USB l ash drive.
Adapters also exist to convert a micro-SD card into a standard full-size SD card.
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