USB flash drive

A SanDisk Cruzer USB drive from 2011, with 4GB of storage capacity.

A USB flash drive[note 1] is a data storage device that includes flash memory with an integrated USB interface. It is typically removable, rewritable and much smaller than an optical disc. Most weigh less than 1 oz (28 grams). Since first appearing on the market in late 2000, as with virtually all other computer memory devices, storage capacities have risen while prices have dropped. As of March 2016, flash drives with anywhere from 8 to 256 GB were frequently sold, while 512 GB and 1 TB units were less frequent.[2][3] As of 2018, 2TB flash drives were the largest available in terms of storage capacity.[4] Some allow up to 100,000 write/erase cycles, depending on the exact type of memory chip used, and are thought to last between 10 and 100 years under normal circumstances (shelf storage time[5]).

USB flash drives are often used for storage, data back-up and transfer 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 immune to electromagnetic interference (unlike floppy disks), and are unharmed by surface scratches (unlike CDs). 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 MB 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, macOS 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.

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. 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

M-Systems, an Israeli company, were granted a US patent on November 14, 2000, titled "Architecture for a [USB]-based Flash Disk", and crediting the invention to Amir Ban, Dov Moran and Oron Ogdan, all M-Systems employees at the time. The patent application was filed by M-Systems in April 1999.[6][1][7] Later in 1999, IBM filed an invention disclosure by one of its employees.[1] Flash drives were sold initially by Trek 2000 International, a company in Singapore, which began selling in early 2000. IBM became the first to sell USB flash drives in the United States in 2000.[1] The initial storage capacity of a flash drive was 8 MB.[7] Another version of the flash drive, described as a pen drive, was also developed. Pua Khein-Seng from Malaysia has been credited with this invention.[8] Patent disputes have arisen over the years, with competing companies including Singaporean company Trek Technology and Chinese company Netac Technology, attempting to enforce their patents.[9] Trek won a suit in Singapore,[10][11] but has lost battles in other countries.[12] Netac Technology has brought lawsuits against PNY Technologies,[13] Lenovo,[14] aigo,[15] Sony,[16][17][18] and Taiwan's Acer and Tai Guen Enterprise Co.[18]

Technology improvements

Flash drives are often measured by the rate at which they transfer data. Transfer rates may be given in megabytes per second (MB/s), megabits per second (Mbit/s), or in optical drive multipliers such as "180X" (180 times 150 KiB/s).[19] 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 (1.5 MB/s) with accounted overhead.[20] The effective transfer rate of a device is significantly affected by the data access pattern.[21]

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 translates to a 35 MB/s effective throughput.[22] That same year, Intel sparked widespread use of second generation USB by including them within its laptops.[23]

Third generation USB flash drives were announced in late 2008 and became available in 2010.[citation needed] Like USB 2.0 before it, USB 3.0 dramatically improved data transfer rates compared to its predecessor. The USB 3.0 interface specified transfer rates up to 5 Gbit/s (625 MB/s), compared to USB 2.0's 480 Mbit/s (60 MB/s).[citation needed] By 2010 the maximum available storage capacity for the devices had reached upwards of 128GB.[7] USB 3.0 was slow to appear in laptops. As of 2010, the majority of laptop models still contained the 2.0.[23]

In January 2013, tech company Kingston, released a flash drive with 1TB of storage.[24] The first USB 3.1 type-C flash drives, with read/write speeds of around 530 MB/s, were announced in March 2015.[25] As of July 2016, flash drives within the 8 to 256 GB were sold more frequently than those between 512 GB and 1 TB units.[2][3] In 2017, Kingston Technology announced the release of a 2-TB flash drive.[26]

Usbkey internals.jpg
Internals of a typical USB flash drive

1 USB Standard-A, "male" plug
2 USB mass storage controller device
3 Test point
4 Flash memory chip
5 Crystal oscillator
6 LED (Optional)
7 Write-protect switch (Optional)
8 Space for second flash memory chip

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 plug, facilitating data transfers between different devices.[27]

Other Languages
Afrikaans: USB-flitsdryf
azərbaycanca: USB fləş kart
башҡортса: USB-флеш-һаҡлағыс
भोजपुरी: पेन ड्राइव
български: USB флаш
bosanski: USB stick
brezhoneg: Alc'hwez USB
català: Memòria USB
čeština: USB flash disk
dansk: USB-nøgle
eesti: Mälupulk
Ελληνικά: Μνήμη USB
español: Memoria USB
Esperanto: USB-poŝmemorilo
euskara: USB memoria
français: Clé USB
galego: Memoria USB
ગુજરાતી: USB ડ્રાઇવ
հայերեն: USB ֆլեշ կրիչ
Արեւմտահայերէն: USB Ցայտիչ
hornjoserbsce: USB-tykač
hrvatski: USB memorija
Bahasa Indonesia: Diska lepas USB
italiano: Chiave USB
latviešu: USB zibatmiņa
Lëtzebuergesch: USB-Späicherstëft
lietuvių: USB atmintukas
lumbaart: Memoria USB
magyar: Pendrive
Bahasa Melayu: Pemacu kilat USB
Nederlands: USB-stick
norsk: Minnepinne
norsk nynorsk: Minnepinne
polski: Pamięć USB
português: USB flash drive
română: Memorie USB
sicilianu: Chiavi USB
Simple English: USB flash drive
slovenčina: Jednotka USB flash
slovenščina: USB-ključ
српски / srpski: USB memorija
srpskohrvatski / српскохрватски: USB stick
suomi: USB-muisti
svenska: USB-minne
тоҷикӣ: Флеш диск
vèneto: Ciaveta USB
Tiếng Việt: Ổ USB flash
吴语: U盘
粵語: USB記憶體
中文: 闪存盘