Pen drive is integrated with USB (Universal Serial Bus) interface. It is a NAND (which stands for `Not and`) type of flash memory technology that excels at reading, writing and erasing data from flash memory. Their size ranges from 1 inch to 4 inches or 2.5 cm to 10 cm. They are much smaller than floppy discs and weighs less than 2 oz.

The storage capacity of a general pen drive ranges between 64 MB to 64GB. While they show a steady increase in storage and price per gigabyte, some pen drives have a capacity of one million re-writes or erase cycles with a ten year data retention capacity when connected to USB 1.1 or USB 2.0.

The major advantages of USB pen drives over other portable storage devices such as floppy discs or DVD/CD is their compact shape and size, they operate faster and can hold more data. As the pen drives are not associated with any moving parts, they operate more reliably.

In recent times, the more updated computers lack floppy disc drives while USB ports appear in every current mainstream PCs and Laptops. Most of the pen drives use the USB mass storage system which can be supported by any modern Operating System such as Windows, Mac OSX, Linux and other Unix oriented systems. Pen drives using USB ports function faster than the optical disk drives.

The pen drive contains a minute circuit board which is protected by plastic, rubberized or metal case. Such sturdy protection shields the pen drive while being carried in the pocket or key chain. The USB connector is shielded by a removable cap or it can be automatically retracted into the body of the drive. This prevents it from being damaged even when exposed.

Most of the normal pen drives use standard A - USB connection. These storage units combine a number of older technologies with low cost, low power consumption and small size possible now by the recent advancements in micro processor technology. The memory storage is based on earlier EPROM and EEPROM technologies.

Hardware designers later developed pen drives which carried their own micro processor system. These are the miniaturized version. This form of miniaturization was facilitated by the development of high speed serial data interface. In computers using pen drive, the controller system has full control over the stored information bank.

However, the actual EEPROM writing and erasing procedures are still quite similar to the earlier mode of operation. The fastest pen drive currently available use dual channel controller. The over all file transfer speed varies considerably and are measured in megabytes or megabits per second. The essential components of a pen drive are male type USB connector, USB mass storage controller, NAND flash memory chip and crystal oscillator controlling the device`s data output.

Additional components are test pins and jumpers, LED`s to indicate data transfer, write protecting switches, unpopulated space, USB connector cap or a cover and a transport aid. The USB pen drives have been integrated into other commonly carried items such as watches, pens and can even be fitted into novelty toy cars.

Their small size and affordable price makes these drives increasingly popular peripherals. Pen drives are primarily used for data transfer, secure data storage in application and software files. They are particularly popular among system and network administrators and also enjoy notable success in PC repair field as a means to transfer data recovery and anti-virus software.