USB flash drive
A USB flash drive is a data storage device that includes flash memory with an integrated USB interface. A typical USB drive is removable, rewritable, and smaller than an optical disc, and usually weighs less than. Since first offered for sale in late 2000, the storage capacities of USB drives have ranged from 8 megabytes to 1 terabyte. As of 2024, 4 TB flash drives were the largest currently in production. Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to physically last between 10 and 100 years under normal circumstances.
Common uses of USB flash drives are for storage, supplementary back-ups, and transferring of computer files. Compared with floppy disks or CDs, they are smaller, faster, have significantly more capacity, and are more durable due to a lack of moving parts. Additionally, they are less vulnerable to electromagnetic interference than floppy disks, and are unharmed by surface scratches. However, as with any flash storage, data loss from bit leaking due to prolonged lack of electrical power and the possibility of spontaneous controller failure due to poor manufacturing could make it unsuitable for long-term archiving of data. The ability to retain data is affected by the controller's firmware, internal data redundancy, and error correction algorithms.
Until about 2005, most desktop and laptop computers were supplied with floppy disk drives in addition to USB ports, but floppy disk drives became obsolete after widespread adoption of USB ports and the larger USB drive capacity compared to the "1.44 megabyte" 3.5-inch floppy disk.
USB flash drives use the USB mass storage device class standard, supported natively by modern operating systems such as Windows, Linux, and other Unix-like systems, as well as many BIOS boot ROMs. USB drives with USB 2.0 support can store more data and transfer faster than much larger optical disc drives like CD-RW or DVD-RW drives and can be read by many other systems such as the Xbox One, PlayStation 4, DVD players, automobile entertainment systems, and in a number of handheld devices such as smartphones and tablet computers, though the electronically similar SD card is better suited for those devices, due to their standardized form factor, which allows the card to be housed inside a device without protruding.
A flash drive consists of a small printed circuit board carrying the circuit elements and a USB connector, insulated electrically and protected inside a plastic, metal, or rubberized case, which can be carried in a pocket or on a key chain, for example. Some are equipped with an I/O indication LED that lights up or blinks upon access. The USB connector may be protected by a removable cap or by retracting into the body of the drive, although it is not likely to be damaged if unprotected. Most flash drives use a standard type-A USB connection allowing connection with a port on a personal computer, but drives for other interfaces also exist. USB flash drives draw power from the computer via the USB connection. Some devices combine the functionality of a portable media player with USB flash storage; they require a battery only when used to play music on the go.
History
The basis for USB flash drives is flash memory, a type of floating-gate semiconductor memory invented by Fujio Masuoka in the early 1980s. Flash memory uses floating-gate MOSFET transistors as memory cells. In 1995, a group of companies including IBM, Microsoft, Intel and NEC were working on the development of Universal Serial Bus.Multiple individuals have staked a claim to having invented the USB flash drive. On April 5, 1999, Amir Ban, Dov Moran, and Oron Ogdan of M-Systems, an Israeli company, filed a patent application entitled "Architecture for a Universal Serial Bus-Based PC Flash Disk" that combined flash memory storage with USB connectors through a USB controller. The patent was subsequently granted on November 14, 2000, and these individuals have often been recognized as the inventors of the USB flash drive. Also in 1999, Shimon Shmueli, an engineer at IBM, submitted an invention disclosure asserting that he had invented the USB flash drive.
Netac Technology filed a patent application for its USB storage device on November 14, 1999, and was granted by the Chinese government in July 2002. Netac went on to obtain another patent in the United States on October 13, 2000, and application was granted on December 7, 2004. Netac's patent was disputed by M-systems and Singaporean company Trek 2000 but Netac remained as the holder of the patent. Netac went on to file legal battles domestically in China and overseas and had received patent royalties and licensing fees in return. The company also invented a feature called "write-protect" function on its USB memory sticks. A Singaporean company named Trek 2000 International is the first company known to have sold a USB flash drive, which it trademarked as "ThumbDrive", and has also maintained that it is the original inventor of the device. Trek 2000 obtained a Singapore patent for the "ThumbDrive" in April 2002. It went on to sue the other four companies for infringing its patent. Singapore High Court ruled in Trek 2000's favour in 2005. After that, Trek 2000 went on to obtain patents from other countries. However, in 2005, Trek 2000 experienced a setback when its USB storage device patent was revoked in the United Kingdom. Pua Khein-Seng, a Malaysian engineer who co-founded a Taiwanese company named Phison, invented a USB drive system on a chip design in 2001 which uses a single chip instead of multiple chips used by its competitiors, which reduces the size and cost of production of flash drives.
Given these competing inventor claims, patent disputes involving the USB flash drive have arisen over the years. Both Trek 2000 International and Netac Technology have accused others of infringing their patents on the USB flash drive. However, the question of who was the first to invent the USB flash drive has multiple claims persists. Netac Technology got the basic American copyright on December 7, 2004. And in the lawsuit, the PNY company paid 7.71 million dollars to Netac.
Technology improvements
Flash drives are often measured by the rate at which they transfer data. Transfer rates may be given in megabytes per second, megabits per second, or in optical drive multipliers such as "180X". File transfer rates vary considerably among devices. Second generation flash drives have claimed to read at up to 30 MB/s and write at about half that rate, which was about 20 times faster than the theoretical transfer rate achievable by the previous model, USB 1.1, which is limited to 12 Mbit/s with accounted overhead. The effective transfer rate of a device is significantly affected by the data access pattern.By 2002, USB flash drives had USB 2.0 connectivity, which has 480 Mbit/s as the transfer rate upper bound; after accounting for the protocol overhead That same year, Intel sparked widespread use of second generation USB by including them within its laptops.
By 2010, the maximum available storage capacity for the devices had reached upwards of 128 GB. USB 3.0 was slow to appear in laptops. Through 2010, the majority of laptop models still contained only USB 2.0.
In January 2013, tech company Kingston, released a flash drive with 1 TB of storage. The first USB 3.1 type-C flash drives, with read/write speeds of around 530 MB/s, were announced in March 2015. By July 2016, flash drives with 8 to 256 GB capacity were sold more frequently than those with capacities between 512 GB and 1 TB. In 2017, Kingston Technology announced the release of a 2-TB flash drive. In 2018, SanDisk announced a 1 TB USB-C flash drive, the smallest of its kind.
On a USB flash drive, one end of the device is fitted with a single Standard-A USB plug; some flash drives additionally offer a micro USB or USB-C plug, facilitating data transfers between different devices.
Technology
Inside the casing is a small printed circuit board, which has some power circuitry and a small number of surface-mounted integrated circuits. Typically, one of these ICs provides an interface between the USB connector and the onboard memory, while the other is the flash memory. Drives typically use the USB mass storage device class to communicate with the host.Flash memory
Flash memory combines a number of older technologies, with lower cost, lower power consumption and small size made possible by advances in semiconductor device fabrication technology. The memory storage is based on earlier EPROM and EEPROM technologies. These had limited capacity, were slow for both reading and writing, required complex high-voltage drive circuitry, and could be re-written only after erasing the entire contents of the chip.Hardware designers later developed EEPROMs with the erasure region broken up into smaller "fields" that could be erased individually without affecting the others. Altering the contents of a particular memory location involved copying the entire field into an off-chip buffer memory, erasing the field, modifying the data as required in the buffer, and re-writing it into the same field. This required considerable computer support, and PC-based EEPROM flash memory systems often carried their own dedicated microprocessor system. Flash drives are more or less a miniaturized version of this.
The development of high-speed serial data interfaces such as USB made semiconductor memory systems with serially accessed storage viable, and the simultaneous development of small, high-speed, low-power microprocessor systems allowed this to be incorporated into extremely compact systems. Serial access requires far fewer electrical connections for the memory chips than parallel access, simplifying the manufacture of multi-gigabyte drives.
Computers access flash memory systems very much like hard disk drives, where the controller system has full control over where information is actually stored. The actual EEPROM writing and erasure processes are, however, still very similar to the earlier systems described above.
Many low-cost MP3 players simply add extra software and a battery to a standard flash memory control microprocessor so it can also serve as a music playback decoder. Most of these players can also be used as a conventional flash drive, for storing files of any type.