What are the main differences between main memory and external memory
This article mainly introduces the main differences between the main memory and the external memory, the article is very detailed, has a certain reference value, interested friends must read it!
The main difference between the main memory and the external memory is that the main memory is used to store programs and data to be used immediately, and the access speed is fast, but the capacity is small and the price is expensive; the external memory is used to store programs and data that are not in use temporarily, with large capacity and low price, but the access speed is slow.
Memory is a memory unit used to store programs and all kinds of data information. Memory can be divided into two categories: main memory (main memory or memory for short) and auxiliary memory (secondary memory or external memory for short). It is the main memory that exchanges information directly with CPU.
Main memory is an important part of computer hardware, its function is to store instructions and data, and can be directly randomly accessed by the central processing unit (CPU). In order to improve the performance and take into account the reasonable cost, modern computers often adopt multi-level storage system. That is, by the cache memory with small storage capacity and high access speed, the main memory with moderate storage capacity and moderate access speed is essential. The main memory stores information by address, and the access speed is generally independent of the address. A 32-bit address can best express the memory address of a 4GB. This is enough for most applications, but it is not enough for some applications with large amount of computation and very large databases, which puts forward the demand for 64-bit structure.
External memory refers to the storage in addition to computer memory and CPU cache, which can still hold data after power off. Common external memories are hard disk, floppy disk, CD, U disk and so on.
The difference between main memory and external memory
The most prominent feature of the main memory is that the access speed is fast, but the capacity is small and the price is expensive; the external memory is characterized by large capacity, low price, but slow access speed.
The main memory is used to store programs and data that are needed immediately; the external memory is used to store programs and data that are not in use temporarily. Information is often frequently exchanged between internal memory and external memory.
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