The composition of the U disk is very simple, mainly consisting of a shell and a movement, among which:
1. movement: the movement includes a PCB+USB main control chip+crystal oscillator+chip resistor, capacitor +USB interface+chip LED (not all U disks) +FLASH chip;
U disk movement
2. Shell: classified by material, including ABS plastic, bamboo, metal, leather case, silicone, PVC software, etc. According to styles, there are card type, pen type, mini type, cartoon type, business type and simulation type. According to the function classification, there are encryption, antivirus, waterproof, intelligent and so on;
3. For some PVCU disks with special shapes, special packaging is sometimes made;
Compared with other portable storage devices (especially floppy disks), flash drives have many advantages: they occupy less space, usually run faster (USB 1. 1, 2.0, 3.0, 3. 1 standard), can store more data, have reliable performance (because there is no mechanical equipment), and can be disconnected when reading or writing. This disk adopts USB mass storage device standard, and has built-in support in modern operating systems such as Linux, Mac OS X, Unix, Windows2000, XP, Win7, Win8, Win8. 1, Win 10.
The flash drive usually adopts ABS plastic or metal shell, and contains a small printed circuit board inside, which makes the flash drive small enough to be put in a pocket like a key chain ornament or strung on a neck rope. Only the USB connector protrudes from the protective case, usually covered by a small cover. Most flash drives use a standard type A USB connector, which allows them to plug directly into the USB port of a personal computer.
To access the data of the flash drive, the flash drive must be connected to the computer; Whether it is a built-in USB controller directly connected to the computer or a USB hub. Only when the USB port is plugged in, the U disk will start, and the required power supply is provided by the USB connection. However, some flash drives (especially high-speed flash drives using the USB 2.0 standard) may need more power, so if they are connected to a USB hub built in the keyboard or screen, these flash drives will not work unless they are directly plugged into the controller (that is, the USB port provided by the computer itself) or an external USB hub. Some USB flash drives are composed of drives and USB flash drives, so it is necessary to distinguish clearly at the end (in DOS/win32 environment).
Advantage analysis
The biggest advantages of U disk are: small and portable, large storage capacity, low price and reliable performance. U disk is very small, only the size of 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 2G, 4G, 8G, 16G, 32G, and 64G( 1GB is gone because of its small capacity), and there are also 128G, 256G, 5 12G,1t. Take the most common 8GB as an example, you can buy it around 20-40 yuan and around 50 yuan 16G. There is no mechanical device in the USB flash drive, 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 are almost impervious to water or dust, and are not scratched, which are serious problems 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, its storage capacity is relatively large. Early flash drives had a small capacity and could only store files of 16-32M. Even so, it is equivalent to 10-20 times the capacity of the floppy disk of the erasable mobile storage medium at that time. With the development of science and technology, the capacity of U disk also grows rapidly according to Moore's law. By 20 12, the 4G USB flash drive is on the verge of elimination, and the capacity of mainstream USB flash drive has developed to 8- 16G, which is equivalent to the capacity of 2-4 DVD discs. The maximum capacity has reached 1T, which is equivalent to the capacity of more than 240 DVD discs.
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.