What is the principle of data storage?

The principle of U disk storage is to add a floating gate and a selection gate to the original transistor to form a floating gate, and store electrons on the semiconductor with unidirectional current conduction between the source and 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. The principle data stored in the hard disk is stored on several disks sealed in the inner cavity of the clean hard disk drive. These disks are usually formed by coating magnetic media on the surface of a substrate with aluminum as the main component. On each side of the disk, several concentric circles with a certain magnetic density as the axis are divided into tracks, and each track is divided into several sectors, and the data is stored on the hard disk according to the sectors. There is a read-write head on each side, so all tracks in the same position of different heads form a so-called cylinder. Traditional hard disk reading and writing is addressed by cylinder, head and sector (CHS addressing). The hard disk rotates at a high speed (above 5400 rpm) after being powered on. The magnetic head on the magnetic head arm is suspended on the surface of the disk, and can be moved between different cylinders by stepping motor to read and write different cylinders. Therefore, if the hard disk vibrates violently when it is powered on, the surface of the disk is easily scratched and the magnetic head is easily damaged, which will bring disastrous consequences to the data stored on the disk. The first sector of the hard disk (1 sector, 0 channel, 0 head) is reserved as the main boot sector. There are two main contents in the main boot area: the main boot record and the hard disk partition table. The master boot record is a piece of program code, whose main function is to boot the operating system installed on the hard disk; The hard disk partition table stores partition information of the hard disk. When the computer starts, it will read the data of the sector to judge its legitimacy (whether the last two bytes of the sector are 0x55AA or 0xAA55). If it is legal, it will jump to execute the first instruction of the sector. Therefore, the main boot area of hard disk often becomes the target of virus attack, and is tampered with or even destroyed. Bootable flag: 0x80 is the bootable partition type flag; 0 means unknown; 1 is fat12; ; 4 is fat16; ; 5 is an extended partition and so on. References:

/Dencayne