What kind of memory is rom?

ROM is read-only memory. Read-only memory works in a non-destructive read-out manner and can only read information but not write it. Once the information is written, it is fixed and will not be lost even if the power is turned off, so it is also called fixed memory.

The operating environment of this article: windows10 system, thinkpad t480 computer.

Read-Only Memory (ROM) works in a non-destructive readout mode and can only read information but cannot write it. Once the information is written, it is fixed and will not be lost even if the power is turned off, so it is also called fixed memory. The data stored in ROM is usually written before being loaded into the whole machine. It can only be read out during the operation of the whole machine. Unlike random access memory, the stored content can be rewritten quickly and conveniently. The data stored in ROM is stable and will not change after a power outage. It has a simple structure and is easy to use, so it is often used to store various fixed programs and data.

Except for a few types of read-only memories (such as character generators) that can be used universally, different types of read-only memories have different functions. In order to facilitate user use and mass production, different types such as programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), and electrified erasable programmable read-only memory (EEPROM) have been further developed. ROM is widely used. The hardware used in the startup program (operating system) of early personal computers such as Apple II or IBM PC XT/AT or the firmware in various other microcomputer systems is ROM.

The characteristic of read-only memory is that it can only read information but cannot write information. Usually, a basic input/output system is solidified in the ROM of the computer motherboard, called BIOS (Basic Input Output System). Its main function is to complete the power-on self-test of the system, initialization of each functional module in the system, basic input/output driver of the system and boot operating system.

Related expansion:

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.

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