The memory in flash drives is commonly engineered with multi-level cell (MLC) based memory that is good for around 3,000-5,000 program-erase cycles,[40] but some flash drives have single-level cell (SLC) based memory that is good for around 100,000 writes. There is virtually no limit to the number of reads from such flash memory, so a well-worn USB drive may be write-protected to help ensure the life of individual cells.
Installers of some operating systems can be stored to a flash drive instead of a CD or DVD, including various Linux distributions, Windows 7 and newer versions, and macOS. In particular, Mac OS X 10.7 is distributed only online, through the Mac App Store, or on flash drives; for a MacBook Air with Boot Camp and no external optical drive, a flash drive can be used to run installation of Windows or Linux.
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Some manufacturers, aiming at a "best of both worlds" solution, have produced card readers that approach the size and form of USB flash drives (e.g., Kingston MobileLite,[65] SanDisk MobileMate[66]) These readers are limited to a specific subset of memory card formats (such as SD, microSD, or Memory Stick), and often completely enclose the card, offering durability and portability approaching, if not quite equal to, that of a flash drive. Although the combined cost of a mini-reader and a memory card is usually slightly higher than a USB flash drive of comparable capacity, the reader + card solution offers additional flexibility of use, and virtually "unlimited" capacity. The ubiquity of SD cards is such that, circa 2011, due to economies of scale, their price is now less than an equivalent-capacity USB flash drive, even with the added cost of a USB SD card reader.
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]
