Various classification criteria, one is the medium according to a storage mode, according to information storage durability, there is the use in a computer system according to points
Classified according to storage
- Random access memory
contents of any memory cell can be randomly accessed, and the access time and the memory unit regardless of physical location. - Sequential memory
can only be accessed in an order, and the access time of the physical location of the storage unit concerned.
By reading and writing functional classification
- ROM
read only, do not allow to change the content, read only memory can not be written while working. - Random access memory
both can read write memory
Information stored by the persistence Category
- Nonvolatile memory
storage information is still stored after a power failure, such as a magnetic storage surface. - Volatile memory
means the information disappears after a power failure of memory, such as read-write semiconductor memory.
By Application
The memory in a computer system role, divided into the main memory, secondary memory, cache memory, a control memory. In order to solve the memory requirements for large capacity, high speed, low cost, conflicts between the three, usually multi-level memory architecture, i.e. the use of the cache memory, a main memory and external memory.
By media classification
Magnetic core memory, a semiconductor memory, a magnetic memory and an optical surface of the memory, of course, there are other types of memories which have different characteristics and adapt their applications.
- The semiconductor memory
using a semiconductor memory device composed. Such registers, cache, memory - Magnetic core memory
with small toroid (ring) to the core thread by writing and reading information. Each point represents the core information. Core can be magnetized bits stored in the core is zero or one in two different ways (clockwise or counterclockwise), depending on the magnetization direction of the magnetic core. A single wire arranged to allow the core to be set to 0 or 1, and its magnetization is changed by sending an appropriate current pulse to the selected wire. The reading process can lead to kernel kernel reset to zero, so as to be erased. This is called destructive reading. When no write operation, even when the power is turned off, the kernel will hold the last values. This makes them non-volatile. It has been replaced. - Magnetic storage surface
of the magnetic surface is coated with a memory using two different magnetization states of the magnetic material in the surface of the carrier to represent a binary "0" and "1" information. The magnetic material is uniformly applied to the magnetic recording medium formed on the substrate, to read and write by the relative movement of the recording head and the Q memory matrix of the memory it is a magnetic surface. Such as hard disk and tape. - Optical storage
using a laser writing and reading information on the medium. Such as CD-ROM and CD-ROM drive.
The main memory classification destination
