What cannot be modified using instructions in the microcomputer's internal memory

In the internal memory of the microcomputer, instructions cannot be used to modify the storage content of the ROM part. The data stored in read-only memory ROM is usually written before being loaded into the whole machine. Once the information is written, it is fixed and can only be read out during the operation of the whole machine. Unlike random access memory, the storage content can be quickly and easily rewritten. 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.

The operating environment of this tutorial: Windows 7 system, Dell G3 computer.

In the internal memory of the microcomputer, instructions cannot be used to modify the storage content of the ROM part.

ROM memory

Read-Only Memory (ROM) works in a non-destructive readout mode and only Can read but cannot write information. 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.

Features

The characteristic of read-only memory is that it can only read information but cannot write information. A basic input/output system is usually solidified in the ROM of the computer motherboard. It's 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.

#There are many types of ROM, and each type of read-only memory has its own characteristics and scope of application. According to its manufacturing process and function, there are five types of ROM, namely mask-programmed read-only memory MROM (Mask-programmed ROM), programmable read-only memory PROM (Programmable ROM), erasable and programmable read-only memory Memory EPROM (Erasable Programmable ROM), electrically erasable programmable read-only memory EEPROM (Electrically Erasable Programmable ROM) and flash erasable read-write memory (Flash Memory).

Scope of use

Since ROM has the characteristic of not losing information after power off, it can be used as the BIOS chip for computer startup. . EPROM, EEPROM and Flash ROM (NOR Flash and NAND Flash) have the same performance as ROM, but can be rewritten. Generally, reading is faster than writing. Writing requires a higher voltage than reading (reading 5V and writing 12V), but Flash can be read at the same voltage. It has large capacity and low cost, and is widely used in MP3 disks such as USB flash drives. In computer systems, RAM is generally used as memory, and ROM is generally used as firmware to store some hardware drivers.

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