The memory device used to store programs and data in a computer is "memory"; memory is divided into two categories. One is the internal memory located in the host, also called main memory, which is used to store the current operation. The programs and data used by the programs belong to temporary memory. The other type is the memory belonging to the computer's external device, called external memory, which is used to store data and programs that are not used temporarily and belongs to permanent memory.
The operating environment of this tutorial: Windows 10 system, DELL G3 computer.
In a computer, the memory device used to store programs and data is a memory.
Computer memory is divided into two categories. One is the internal memory located in the host, also called main memory. It is used to store the currently running program and the data used by the program. It is a temporary memory. Such as memory sticks.
The second is the memory belonging to the external device of the computer, called external memory, referred to as external storage, also called auxiliary storage (referred to as auxiliary storage) such as hard disk, U disk, etc. The external memory stores data and programs that are not used temporarily. It is a permanent memory and should be transferred into the memory when needed.
What is internal memory
Internal memory is what we call memory. Storage inside the CPU or on the motherboard. The one inside the CPU is called cache, which is used for internal data processing of the CPU. There are two types on the motherboard. One is called ROM, which is read-only memory. It records and stores various hardware information of the host, system boot mode, clock and other information. This information is generally fixed at the factory and is not allowed to be changed at will, so the information can only be read out, not written.
Extended knowledge: working principle
Memory is a collection of many storage units, arranged in order of unit numbers. Each unit is composed of a number of binary bits to represent the value stored in the storage unit. This structure is very similar to the structure of an array, so in the VHDL language, the memory is usually described by an array.
Memory is a memory component used to store programs and various data information. Memory can be divided into two categories: main memory (referred to as main memory or memory) and auxiliary memory (referred to as auxiliary memory or external memory). It is the main memory that directly exchanges information with the CPU.
The working method of main memory is to store or read various types of information according to the address of the storage unit, collectively referred to as access memory. The carrier that collects storage units in the main memory is called a memory bank. Each unit in the memory bank can store information represented by a string of binary codes. The total number of bits of this information is called the word length of a storage unit. There is a one-to-one correspondence between the address of the storage unit and the information stored in it. There is only one unit address, which is fixed, but the information stored in it can be replaced.
The binary code indicating each unit is called the address code. When looking for a certain unit, first give its address code. The register that temporarily stores this address code is called the memory address register (MAR). In order to store information taken out from the storage unit of the main memory or information to be stored in a certain storage unit, a memory data register (MDR) is also set up.
Features
The computer’s memory can be divided into internal memory and external memory. Internal memory is used frequently by the computer during program execution and is directly accessible during an instruction cycle. External storage requires the computer to read information from an external storage device such as a tape or disk. This is similar to students taking notes in class. If the student knows the content without looking at the notes, the information is stored in "internal memory." If a student must consult notes, the information is in "external memory."
There are many types of internal memory. Random access memory (RAM) is used as a high-speed scratchpad memory area during computation. Data can be stored in RAM, read and replaced with new data. RAM is available when the computer is running. It contains information placed on the problem that the computer is working on at the moment. Most RAM is "volatile," meaning information will be lost when the computer is turned off. Read-only memory (ROM) is stable. It is used to store the set of instructions that the computer needs when necessary. The information stored in ROM is "hardwired" (i.e., it is a physical part of the electronic component) and cannot be changed by the computer (hence the name "read-only"). Variable ROM is called programmable-only. Read memory (PROM), which can be changed by exposing it to an external electrical device or optical device (such as a laser).
The internal memory in a digital imaging device must be large enough to store at least one digital image. A 512 x 512 x 8-bit image requires 1/4 megabyte. Therefore, an imaging device processing several such images will require several megabytes of memory.
External memory is used to store images that are not acquired during real-time imaging tasks. It has a different level of separation from the computer. Images where a diagnosis has been made are often stored for years for legal purposes. These images are called "archives" (such as tapes), and they must be reinstalled on the computer to retrieve the information. Images on the hard drive are physically installed on the computer and can be accessed within milliseconds. Individual bits in magnetic memory are recorded as magnetic domains, where "North Pole up" might mean a 1, and "North Pole down" might mean a 0.
The most commonly used external memory devices store information in one of two ways. Magnetic tape, which was a mainstay of computer storage in the 1970s in the form of large reel-to-reel devices, is now a relatively cheap "offline" storage option in the form of small, enclosed cartridges. Although it may take seconds or even minutes to load modern audio tapes and find where the data of interest is stored, the long-term cost of purchasing and maintaining this storage medium is low.
A variety of optical memory devices are also available. The time required to access a particular sequence of data in an optical memory device may be as short as the time required to access data on a (magnetic) hard drive. There are tiny defects on one of the smooth mirror surfaces of the disc. Burning a hole on the surface of the disc represents the binary number 1, while burning no holes represents 0. The fired disc is an example of a "write once, read many" (WORM) disc. This feature makes them suitable for long-term file storage while maintaining high access rates. The 12 cm diameter disc has become the standard for music recording and general PC use. These disks are called "high-density disks" or CD ROMs. A high-capacity disc that is the same size as a CD ROM but can store enough digital information to support several hours of high-quality video is called a digital video disc (DVD). DVDs are becoming popular. Mechanical devices are sometimes used on request to extract and mount discs from a large batch of discs. These devices were called "jukeboxes."
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