The advantages of editing this paragraph
The biggest advantages of U disk are: small and portable, large storage capacity, low price and reliable performance. The USB flash drive is very small, only the size of a thumb, and its weight is extremely light, generally around 15g. Especially suitable for carrying around. We can hang it on our chests, on key chains, or even in our wallets. Generally, the capacities of USB flash drives are 1G, 2G, 4G, 8G, 16G, 32G, etc. Take the most common 4GB as an example, you can buy it around 50 yuan. There is no mechanical device in the warehouse, which has strong seismic performance. In addition, the USB flash drive has the characteristics of moistureproof, antimagnetic, high and low temperature resistance, and has good safety and reliability. * Flash drives will hardly be infiltrated by water or dust, and will not be scratched, which are serious problems existing in old portable storage devices (such as optical disks and floppy disks). The solid-state storage design used in flash drives enables them to withstand unintentional external shocks. These advantages make flash drives very suitable for carrying personal data or work files from one place to another, such as from home to school or office, or generally speaking, various places where personal data need to be carried and accessed. Because USB is almost ubiquitous in today's personal computers, flash drives can be used anywhere. However, the small size of flash drives also makes them often misplaced, forgotten or lost. * Although the flash drive is small, it has a relatively large storage capacity. At present, most flash drives on the market can store more data than a CD(700MB), and advanced ones can store more data than a double-sided and double-layered DVD( 17GB). * Flash drives use a large number of USB storage devices, which means that most modern operating systems can read and write flash drives without installing additional drivers. Flash disk is displayed as a block-like logical unit in the operating system, which hides the complex details needed by internal flash memory. The operating system can use any file system or block addressing. You can also make a boot USB flash drive to start the computer. * Like other flash devices, flash drives have a limit on the total number of reads and writes. Under normal use, the mid-range flash drive can read and write hundreds of thousands of times, but when the flash drive becomes old, the writing operation will take more time. We must consider this when we use flash drives to run applications or operating systems. Some developers have written special versions of operating system (such as Linux) or application programs (such as Mozilla Firefox) for flash drives. They usually optimize the use of space and store temporary disks in the computer's main memory instead of flash drives. * Many flash drives support write protection. This switch on the shell can prevent the computer from writing or modifying data on the disk. Write protection can prevent computer virus files from being written into flash drives, thus preventing the spread of viruses. Flash drives without write protection function, with automatic operation and other functions, have become a way for many viruses to spread. * Flash drives can withstand external shocks better than mechanical disks, but they may still fail or lose data due to serious physical damage. When assembling a computer, the wrong USB connection port wiring may also damage the circuit of the flash drive.
Edit the storage principle of this paragraph.
The computer converts the binary digital signal into a composite binary digital signal (adding instructions such as allocation, check and stack) and reads it into the USB chip adapter interface. The chip processes the signal and stores the binary data at the corresponding address assigned to the EEPROM memory chip, thus realizing data storage. The control principle of EEPROM data storage is that the voltage of the gate transistor is controlled by the voltage, and the junction capacitance of the gate transistor can store the voltage value for a long time. The main reason for saving data after power failure is that floating gate and selection gate are added to the original transistor. A floating gate for storing electrons is formed on a semiconductor with unidirectional current conduction between the source and the drain. The floating gate is wrapped by a silicon oxide film insulator. Above it is a select/control gate that controls the conduction current between the source and the drain. Whether the data is 0 or 1 depends on whether there are electrons in the floating gate formed on the silicon substrate. One electron is 0, and none is 1. Flash memory, as its name implies, deletes data for initialization before writing. Specifically, electrons are extracted from all floating gates. Some data will return to "1". Write only when the data is 0, and do nothing when the data is 1 When writing 0, a high voltage is applied to the gate electrode and the drain electrode, which increases the electron energy conducted between the source electrode and the drain electrode. In this way, electrons will break through the oxide film insulator and enter the floating gate. When reading data, a certain voltage is applied to the gate electrode, the current is 1, and the current is 0 if it is small. When there are no electrons in the floating gate (data is 1), when a voltage is applied to the gate electrode, a voltage is applied to the drain, and a current will be generated between the source and the drain due to the movement of a large number of electrons. But when there are electrons in the floating gate (data is 0), the electrons conducted in the channel will decrease. Because the voltage applied to the gate electrode is absorbed by the floating gate electrons, it is difficult to affect the channel.
Edit this history of invention
From 1998 to 2000, many companies claimed that they were the first to invent USB flash drives. Include China Netac Technology, Israeli M-Systems and Singapore Trek Company. However, the real patent for the basic invention of U disk is China Netac. In July 2002, Netac's "Flash electronic external storage method and device for data processing system" (patent number: ZL 99 1 17225.6) was officially authorized by China National Intellectual Property Administration. This patent fills the gap of invention patent in the field of computer storage in China for 20 years. The acquisition of this patent right has caused a great shock to the entire storage industry. Including Israeli M-Systems, immediately filed an invalid reexamination with China National Intellectual Property Administration, China, which once became a patent dispute that shocked China and foreign countries in the global flash memory field. However, on February 7, 2004, 65438, Netac obtained the basic invention patent of flash disk officially authorized by the US National Patent Office, with the US patent number of US6829672. The acquisition of this patent right finally ended the struggle. China Netac is the world's first inventor of USB flash drive. On February 10, 2006, Netac entrusted American lawyer Morgan Lewis to file a lawsuit in the eastern federal district of Texas.
The court filed a lawsuit accusing PNY Company of infringing Netac's U.S. patent (U.S. Pat.No. US6829672). In February 2008, Netac and PNY reached an out-of-court settlement. Netac signed a patent license agreement with PNY, and PNY paid Netac a patent license fee of $654.38+million. This is the first time that a China enterprise has obtained a huge patent license fee in the United States, which further proves that Netac is the global inventor of U disk. Now all flash drives support USB2.0 standard; However, due to the technical limitation of NAND flash memory, their reading and writing speed can not reach the maximum transmission speed of 480Mbit/s supported by the current standard. At present, the fastest flash drive has used dual-channel controller, but compared with the hard disk of the present era, or the maximum transmission rate that USB2.0 can provide, it is still a little worse. At present, the highest transfer rate is about 20-40MB/s, while the general file transfer rate is about 100 MB/s, and the transfer rate of older 12Mbit/s devices is only about 1MB/s at most. Among them, the industry leaders are Netac Shenzhen, M-Systems and Trek Singapore.
Future development
Semiconductor manufacturers strive to integrate the functions of various flash drives into a single chip to reduce the cost of flash drive components, thus reducing the overall cost. In order to increase the capacity, 1GB and smaller flash drives are no longer produced. Kanguru recently released a USB2.0 flash drive with 16GB, and claimed that it can store data of 10 years. Lexar is trying to launch a USB flash card. Compatible with USB flash drive, which is expected to replace all kinds of flash cards. (Completed) Sandisk has released a new technology to control the use of copyrighted data on flash drives. The main users of this technology are students. This technology is called FlashCP. Kingston Technology has developed a flash drive, which has the largest storage capacity in the world, up to 256GB.