There are many types of software devices!!!!
some of them include:
- USB Flash drives


A USB flash drive
A USB flash drive
external image magnify-clip.pngA USB flash drive
USB flash drives are NAND-type flash memory data storage devices integrated with a USB (universal serial bus) interface. They are typically small, lightweight, removable and rewritable. As of April 2007, memory capacities for USB Flash Drives currently are sold from 32 megabytes up.
USB flash drives offer potential advantages over other portable storage devices, particularly the floppy disk. They are more compact, faster, hold more data, and are more reliable due to their lack of moving parts, and more durable design. Additionally, it has become increasingly common for computers to ship without floppy disk drives. USB ports, on the other hand, appear on almost every current mainstream PC and laptop. These types of drives use the USB mass storage standard, supported natively by modern operating systems such as Windows, Mac OS X, Linux, and Unix.
A flash drive consists of a small printed circuit board typically in a plastic or metal casing, making the drive sturdy enough to be carried about in a pocket, as a key fob, or on a lanyard. Only the USB connector protrudes from this protection, and is usually covered by a removable cap. Most flash drives use a standard type-A USB connection allowing them to be connected directly to a port on a personal computer.
To access the data stored in a flash drive, the drive must be connected to a computer, either by plugging it into a USB host controller built into the computer, or into a USB hub. Flash drives are active only when plugged into a USB connection and draw all necessary power from the supply provided by that connection. However, some flash drives, especially high-speed drives, may require more power than the limited amount provided by a bus-powered USB hub, such as those built into some computer keyboards or monitors. These drives will not work unless plugged directly into a host controller (i.e., the ports found on the computer itself) or a self-powered hub.

external image 350px-Usbkey_internals.jpg
Internals of a typical flash drive
(Saitek brand USB1.1 pictured)

USB connector
USB mass storage controller device
Test points
Flash memory chip
Crystal oscillator
Write-protect switch
Space for second flash memory chip

Common uses

System administration Flash drives are particularly popular among system and network administrators, who load them with configuration information and software used for system maintenance, troubleshooting, and recovery. Computer repair Flash drives enjoy notable success in the PC repair field as a means to transfer recovery and antivirus software to infected PCs, while allowing a portion of the host machine's data to be archived in case of emergency. Application carriers Flash drives are used to carry applications that run on the host computer without requiring installation. U3, backed by flash drive vendors, offers an API to flash drive-specific functions. A free and open-source software platform known as Portableapps has also been developed to allow U3-like functionality on non-U3 drives. airWRX is an application framework that runs from a flash drive and turns its PC host and other nearby PCs into a multi-screen, web-like work environment. pocketSAN is a portable iSCSI framework that runs from a flash drive and turns its PC host into a full-featured SAN appliance. The Mozilla Firefox browser has a configuration for flash drives, as does Opera.[9][10]
A Creative MuVo, a small solid-state digital audio player in a flash drive form
A Creative MuVo, a small solid-state digital audio player in a flash drive form
external image magnify-clip.pngA Creative MuVo, a small solid-state digital audio player in a flash drive formTo boot operating systems In a way similar to that used in LiveCD, one can launch any operating system from a bootable flash drive, known as a LiveUSB. Windows Vista ReadyBoost In Windows Vista, the ReadyBoost feature allows use of some flash drives to augment system memory. Personal data transport The most common use of flash drives is to transport and store personal files such as documents, pictures and video. Individuals also store medical alert information on MedicTag flash drives for use in emergencies and for disaster preparation. Audio players Many companies make solid state digital audio players in a small form factor, essentially producing flash drives with sound output and a simple user interface. Music storing USB key without player (called raw USB memory) can be played in a Hi-Fi or Radio-CD with a USB port. The file formats of the music in the USB key are MP3 or Ogg. In 2004, the German band WIZO made a recording industry first of releasing the "Stick EP", an album available only as a USB drive preloaded with high-bitrate MP3s. In 2007, a product known as the MU-STIK appeared in the market, offering a means of packaging music albums by containing all relevant digital audio/video data and a customizable player interface within a USB key.[11]In arcades In the arcade game In the Groove and more commonly In The Groove 2, flash drives are used to transfer high scores, screenshots, dance edits, and combos throughout sessions. While use of flash drives is common, the drive must be Linux compatible, causing problems for some players. Data used can then be uploaded to Groovestats.

Flash drives are nearly impervious to the scratches and dust that were problematic for previous forms of portable storage, such as compact discs and floppy disks, and their durable solid-state design means they often survive casual abuse. This makes them ideal for transporting personal data or work files from one location to another, such as from home to school or office or for carrying around personal data that the user typically wants to access in a variety of places. The near-ubiquity of USB support on modern computers means that such a drive will work in most places. A drawback to the small size is that they are easy to misplace, leave behind, or otherwise lose, leading to the practice of attaching them to keychains or necklaces.
Flash drives are also a relatively dense form of storage, where even the cheapest will store dozens of floppy disks worth of data. Many can hold more data than a CD (700 MB). Top of the line flash drives can store more data than a DVD.
Flash drives implement the USB mass storage device class, meaning that most modern operating systems can read and write to flash drives without any additional device drivers. The flash drives present a simple block-structured logical unit to the host operating system, hiding the individual complex implementation details of the various underlying flash memory devices. The operating system can use whatever type of file system or block addressing scheme it wants. Some computers have the ability to boot up from flash drives.
Flash drives are much more tolerant of abuse than mechanical drives, but can still be damaged or have data corrupted by severe physical impacts. Improperly wired USB ports can also destroy the circuitry of a flash drive, a danger in home-built desktop PCs.
Some flash drives can retain their memory after being submerged in water [12], even through a machine wash. Leaving the flash drive out to dry completely before allowing current to run through it has been known to result in a working drive with no future problems.

[edit] Weaknesses

Like all flash memory devices, flash drives can sustain only a limited number of write and erase cycles before failure. Mid-range flash drives under normal conditions will support several hundred thousand cycles, although write operations will gradually slow as the device ages. This should be a consideration when using a flash drive to run application software or an operating system. To address this, as well as space limitations, some developers have produced special versions of operating systems (such as Linux) or commonplace applications (such as Mozilla Firefox) designed to run from flash drives. These are typically optimized for size and configured to place temporary or intermediate files in the computer's main RAM rather than store them temporarily on the flash drive.
Most USB flash drives do not include a write-protect mechanism, although some have a switch on the housing of the drive itself to keep the host computer from writing or modifying data on the drive. Write-protection makes a device suitable for repairing virus-contaminated host computers without risk of infecting the USB flash drive itself.
In some USB flash drives, the USB interface is bigger than the storing body.
NAND flash memory devices many times are made with less than suitable components. There are many companies that sell these USB storage devices using these less than standard parts. These devices fail more often than larger name manufacturers. Information on the advanced circuits or circuit damage repairs regarding the NAND or electronics surrounding the NAND wafers on board USB devices can be found by contacting eProvided