Hardware Reference
In-Depth Information
Because USB flash drives are physically small, very portable, and capable
of retaining large quantities of data, they're considered by many industry
experts to be a serious security risk. Some organizations prohibit staff from
using these devices on their systems. There have been widely reported cases
of USB flash drives being found in public places with sensitive data on them.
Some USB flash drives come with additional encryption, rendering the data
useless to anyone except the authorized user.
Flash Memory Cards and Readers
A fl ash memory card
contains the same fl ash RAM as a USB fl ash drive except that it's in a
different kind of packaging. Instead of being on a stick-like USB device, it's embedded in a thin
plastic cartridge with metal contacts that fi t up against the metal contacts in a card reader.
Many non-computer devices use fl ash RAM cards to store data for eventual transfer to a
computer. For example, digital cameras, digital video recorders, and some medical devices
such as blood pressure and blood sugar meters store their output on fl ash RAM cards.
Because there is no port built into a fl ash memory card, it must be placed in a card
reader, which is like a disk drive except that it reads memory cards instead of disks. Some
computers have built-in card readers, and you can also buy external card readers that
connect to a PC's USB port. Built-in card readers typically use the same data bus as hard
disks, so data transfer is fast. External card readers are limited to the USB data-bus speed,
as are USB fl ash drives. Figure 2.12 shows an example of a card reader that supports
multiple card types.
FIGURE 2.12
An external multicard reader
Photo credit: King of Hearts, Wikimedia Commons
Several different sizes and shapes of fl ash memory cards are available, each with its own
specifi cations and features. Some card readers can accept only one type of card; others can
read and write multiple card types. Some of the common card types include CompactFlash
(CF), SmartMedia (SM), MultiMediaCard (MMC), Secure Digital (SD), Memory Stick, and
xD. Figure 2.13 shows a Secure Digital card.
