storage methode
Storage processes are processes with which information is stored on a physical storage medium. They are physical processes that change the physical states in the storage media. These include the remanence of magnetized particles, holding a voltage potential in a capacitor or changing light reflections. In the early years of storage technology, mechanical storage methods were also used. Holes were punched in punched cards or punched tape, for example.
The remanence of magnetized metal particles
Magnetic memories are among the oldest storage technologies. They work with magnetic tapes on which iron oxide or chromium dioxide particles are deposited. The oxide crystals are magnetized and aligned by a magnetic field and persist in their remanence. The stored information is in the alignment of the oxides and is read out by read/write heads.
The remanence-based storage method was also used in core memories in the past. In this process, smallest ferrite beads, which had a pronounced hysteresis, were magnetized. They persisted in their remanence, which was read out via a read line. Each individual ferrite bead could store two states.
Another magnetic storage method stores information by means of magnetic polarization. This method is used in magnetoelectric random access memories, MRAMs. There is also the ferroelectric storage method, in which the crystal structure of certain materials is changed by electric fields.
Semiconductor-based memory processes
The first memory cells based on semiconductors were flip-flops, multivibrators or flip-flops. They could be used to map two stable voltage states. Later, switching transistors with downstream capacitors, in which the switching state is stored, were used as memory cells. Further development led to flash memories, which are equipped with a special electrode, the floating gate, on which the charge is stored. Similar is the structure of charge- trap flash( CTF), which are used in NAND flashes and have a higher storage density than floating-gate memories.
Magneto-optical storage processes
In magneto-optical( MO) memories, two physical quantities act to store information: Magnetism and light or heat. In principle, the uniformly aligned magnetic information layer is first exposed to a magnetic field that causes no change at normal temperature.