The memory unit is actually a type of sequential logic circuit. According to the type of memory usage, it can be divided into read-only memory (ROM) and random access memory (RAM). The functions of the two are quite different, so their descriptions are also different.
The storage media that make up the memory mainly uses semiconductor devices and magnetic materials. The smallest storage unit in memory is a bistable semiconductor circuit or a CMOS transistor or a storage element of magnetic material, which can store a binary code. A storage unit is composed of several storage units, and a memory is composed of many storage units.
There are several different classification methods of memory based on the performance of the storage material and how it is used. (Recommended learning:web front-end video tutorial)
1. Classification by storage media
Semiconductor memory: a memory composed of semiconductor devices.
Magnetic surface memory: A memory made of magnetic materials.
2. Classification by storage method
Random access memory: The contents of any storage unit can be randomly accessed, and the access time has nothing to do with the physical location of the storage unit.
Sequential memory: It can only be accessed in a certain order, and the access time is related to the physical location of the storage unit.
3. Classification according to the read and write functions of the memory
Read-only memory (ROM): a semiconductor memory whose stored content is fixed and can only be read but not written.
Random read-write memory (RAM): Semiconductor memory that can be both read and written.
4. Classification according to the storability of information
Non-permanent memory: memory in which information disappears after power failure.
Permanent memory: memory that can still retain information after power is turned off.
5. Classified by its role in the computer system
Main memory (memory): used to store active programs and data, with high speed, small capacity, and high price per bit.
Auxiliary memory (external memory): It is mainly used to store currently inactive programs and data. It has slow speed, large capacity and low price per bit.
Buffer memory: Mainly plays a buffering role in two components with different working speeds.
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