How Does a USB Flash Drive Work?

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How Does a USB Flash Drive Work?

USB stands for 'Universal Serial Bus' and is an industry standard adopted in the mid-1990s for defining connectors, cables, and communication protocols used in a bus. A USB flash drive is a popular and easy-to-use digital data storage device that is quite small in size as compared to a floppy disk. Other names for flash drive include key drive, pen drive, jump drive, thumb drive, memory stick, or simply a USB. A USB flash drive consists of flash memory, a type of computer chip that is non-volatile, and an integrated USB interface. A USB 'plug' on the USB flash drive connects it with a USB 'port' on another electronic device.

Typical USBs are rewritable, removable, and weigh less than 30 grams. The number of write and erase cycles for some models go up to 100,000, and the shelf shortage life can be up to 10 years. Maximum storage capacity of a USB flash drive has reached the 1 TB mark, as of the first quarter of 2013.

General knowledge of the operation of a USB flash drive, including its applications, construction, and types, is essential for a buyer to make an informed purchasing decision. These drives can be acquired from computer shops as well as online from the comfort of one's home. eBay, for example, offers an enormous collection of USB flash drives with numerous specifications.

Flash Memory

Flash memory can hold data for very long periods of time without the need for electric power. It can be electronically erased and reprogrammed very easily. The number of applications it is used in is ever increasing. Some of the most notable applications include PDAs, memory cards, digital cameras, game consoles, mobile phones, and, of course, USB flash drives.

USB Interface

The USB interface is the 'plug' on a USB flash drive that connects it to a computer or other electronic device, provided there is a USB 'port' or slot on the receiving end. USB ports are built into the hardware of recent models of most desktop PCs and laptops, a sure sign of the growing popularity of USB flash drives.

Floating-Gate Transistor

A floating-gate transistor is similar to a 'metal oxide semiconductor field effect transistor' (MOSFET) but has two gates instead of one. The top gate is called the 'control gate', while the bottom gate is known as a 'floating gate'. The latter is insulated with an oxide layer completely. In a USB flash drive, every memory cell is a floating-gate transistor. Depending on whether a memory cell is holding an electron or not, it makes up a '1' or '0' in binary code.

Quantum Tunnelling for Erasing Data

For erasing data from a USB flash drive, the process of 'quantum tunnelling' is used. In this method, a strong opposite charge is applied to the top (control) gate of a floating-gate transistor. An electron, as a result, tunnels through the oxide insulation, and the memory cell returns to a '1' in binary code, which means it is empty. Older models required a user to erase the drive completely, but with the advancement of technology, a user now has the option of picking and choosing which files to erase.

Advances in USB Flash Drive Technology

EPROM and EEPROM were the early technologies that memory storage was based on. There were several limitations in the use of these technologies, such as the slow reading and writing speeds, limited capacity, requirement of a high-voltage circuitry drive, and the inability to rewrite a specific portion of a chip because older technology required completely erasing the entire content before rewriting anything. Technological developments have led to the ability to erase single files without affecting other data. The erasure region can now be broken into small-sized 'fields' that can easily be erased individually. In the earlier case, when a user wanted to change the contents of a certain memory location, the entire field had to be copied into an off-chip buffer memory, followed by erasing the field and altering the data as required in the buffer, and finally rewriting the data into the field again.

Additional drivers are generally not required to run USB flash drives as they implement the 'USB mass storage device class'. Computers access and recognise flash drives very much like hard disk drives, and the controller system has full control over the place of information storage. After the USB flash drive has been plugged in, it enters an emulation mode in which it emulates a hard disk drive. The data transfer between the computer and the flash drive gets easier as a result.

Components of a USB Flash Drive

A typical USB flash drive has several components. Some of them are essential for its operation, and others can be regarded as add-ons or additional components. Essential components of a flash drive include a standard-A USB plug that acts as the USB interface to the host device, a USB mass storage controller (a small microcontroller with some RAM and on-chip ROM), NAND flash memory chips for storing data, and a crystal oscillator for generating a 12 MHz clock signal and controlling the data output of the device through a phase-locked loop.

Popular add-ons include LEDs for indicating data reads, writes, and transfers, write-protect switches, jumpers and test pins, USB connector cap for reducing the risk of damage, unpopulated space, and transport aids (body or cap containing a hole for connection to a lanyard or keychain). Expandable storage is also offered by some USB flash drives via a slot for internal memory cards.

Reading, Writing, and Retrieving

One of the greatest benefits of using a USB flash drive is its plug-and-play nature. The driver that supports the USB flash drive instructs the USB port to query the flash drive as soon as a user plugs in the drive. A command is thus sent to the flash drive to perform a read request. The file system is then read, and the information is sent to the computer via the USB port. The driver carries out the interpretation task and forwards the information to the rest of the computer for use.

Upon opening a specific file, the read process is initiated once more. The program sends the specific file location to the USB port, which requests the flash drive for the desired location. Another 'read' is performed, and the file content is returned in a binary format representing the content. The binary data is then returned to the USB port. The driver interprets the data and sends it to the program for output on the screen.

Writing is similar to reading, but in this case, instead of requesting a location, the program writing the file converts it into a binary format, which is then sent to the USB port for forwarding it to the flash drive for writing. Once the process is completed, the computer requests a fresh copy of the layout so that it can easily access the newly written file in the future.

Buying a USB Flash Drive on eBay

Start the USB flash drive hunt from the eBay home page, which is a convenient way of getting down to the desired product in no time. Enter your query into the search bar and shortlist the results based on your personal preferences by simple selection of various filter and category options. For some search terms, eBay suggests some related searches as well that may facilitate the buying process. Some search terms for this example could be USB flash drive, flash drive, and USBs.

Always remember to begin the hunt using your locality as a filter so you can save on delivery charges if you are lucky enough to find the item you want in your area. This can easily be done by entering your postcode on the results page. In a successful case scenario where you find the product locally, you can pick up the order at a convenient time as soon as the order is successfully processed. Another recommended practice is to go through the feedback and reviews to get a better feel for the seller and his or her business practices.


'Universal Serial Bus' (USB) is an industry standard for communicating with a computer, while a 'USB flash drive' is a popular and easy-to-use data storage device. It has several common names, including jump drive, thumb drive, memory stick, pen drive, key drive, or simply a USB. It uses flash memory and an integrated USB interface, hence the term USB flash drive. The USB 'plug' on a flash drive connects it with the USB 'port' on another device, such as a computer.

The storage capacity of USB flash drives is increasing at a rapid pace with advancements in technology. As of the first quarter of 2013, the storage capacity has reached the 1 TB mark. Several components of a USB flash drive are essential to its operation, while others can be regarded as add-ons and extra features that vary from model to model. Understanding USB flash drives and personal needs is critical to choosing the right drive. USB flash drives can be purchased at computer hardware stores as well as online. eBay features a huge selection of USB flash drives for a variety of needs.

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