USB Flash Drive
A USB flash drive is a flash memory data storage device that is integrated with a Universal Serial Bus. USB flash drives are most often removable and rewritable, and are much smaller than other portable storage devices. They are usually used for similar purposes that floppy disks were. Flash drives use the USB mass storage standard that is supported by most modern operating systems such as Windows and Mac OS X. The first USB flash drives were sold commercially in 2000. Aside from physical damage, the flash memory is usually good for about 100,000 writes. The connector can withstand roughly 1,500 connect/disconnect cycles.
A flash drive is made up of a small printed circuit board that carries the circuit elements and a USB connector. It is electrically insulated and protected inside a case that can be carried in a pocket or on a key chain. The USB connector may have a removable cap or retract into the case to protect it. Most flash drives use a standard type-A USB connection and draw their power from the connection. There are four important parts to a flash drive. The male type-A USB connector provides a physical interface to the host computer. A USB mass storage controller employs the USB host controller, which contains a small microcontroller. A NAND flash memory chip stores data, and a crystal oscillator creates the device’s main clock signal and controls the device’s data output. The flash drive may also include jumpers and test pins for testing purposes, LEDs to indicate when data is being used, a transport aid that connects to a key chain, and expandable storage. The most common use of flash drives is for personal transport and storage of personal files. However, flash drives are especially popular among system and network administrators because they can be easily loaded with configuration information and software. They can also be used as application carriers to avoid unnecessary installations, in computer forensics and law enforcement to search for and extract evidence on computers, and for booting operating systems on PCs.
There are both advantages and disadvantages that come along with flash drives. One benefit to using a flash drive for data storage is that the data is resistant to scratches and dust and can be transported easily and safely. Flash drives use very little energy, are small and light, and are not very fragile. They implement the USB mass storage device class so that most modern operating systems can read and write to them without having to install device drivers. A notable disadvantage, however, is that they can only sustain a certain number of write and erase cycles before they fail. They also have space limitations and most of them do not include a write-protect mechanism, making them susceptible to becoming infected by a virus on a host computer. Some users find that because of their size they are easily misplaced or lost. This can become a serious problem if the data is sensitive and needs to be secured.