Difference between random access and permanent memory.

The internal memory of a computer is divided into operative and permanent memory. Unlike the external one, which is represented by plug-in devices HDD, USB-flash, SD-cards, optical disks, it is one of the main elements of the system that ensures its operation. Devices of this type are located directly on the motherboard and do not require user access to them. Let's see how RAM differs from permanent memory.

  1. Comparison
  2. Table

Random access memory (RAM) - volatile variable random access memory, which stores data processed by the processor at a particular time. It is implemented as random access memory and is often referred to simply as RAM.


Read-only memory (ROM) is a non-volatile memory that stores immutable data. It is implemented in the form of microcircuits soldered on the board, which are called read-only memory devices.


ROM is often confused with storage devices where users write files. In fact, this memory is not available to them: the ROM contains BIOS and other microprograms designed to control the interaction of hardware elements, and in mobile devices there is also an operating system. Technically, ROMs also include CD-ROMs, magnetic tapes, punched cards and other media with once placed information, but, of course, they are not part of the computer's internal memory system.


Imagine that you are writing, for example, a report. To read an article, you get up, go to the closet, pick up a book or magazine, carry it at the table, look for information, close it, carry it back, put it on the shelf. And so over and over again. Slow and uncomfortable, especially if the closet is in another room. And if you sit down at a large free desk? Here you have three magazines open on the necessary pages, here is the volume of the encyclopedia, there is a manual, and on the monitor is a browser with links to literature. Everything is available, just reach out and read. In the same way, files of running programs and open documents are stored in RAM. Compared to drives, even the most promising ones, RAM is much faster, the access time is measured in nanoseconds.

RAM is used in computer operations after it is started and the OS is loaded. Data is read from ROM mainly during system startup, and applications do not access them. Recording information into permanent memory can be either factory (ROM itself), or one-time programmable (PROM, in everyday life, manipulation is called "firmware").

The main technical difference between random access memory and permanent memory is volatility. When the power is turned off, the RAM is completely cleared of data, no matter how much of it and no matter how important it may seem. Everyone at least once got into a situation when, while working at the computer, the light suddenly turned off, and then changes in the document, open pages in the browser, the playing video were not saved. This is because before the new revision is written to external memory, it is stored in the operational memory, which, being de-energized, is reset to zero.

Non-volatile memory. A complete power off does not affect its content in any way, therefore programs launched from ROM (BIOS, POST, OS) require only a single write.

If we compare, for example, the process of typing in an editor and uploading firmware or updating to a smartphone, it is noticeable what is the difference between RAM and permanent memory. Symbols appear on the screen immediately (RAM is used), and in the second case it will take several minutes, and sometimes hours (written in ROM).

Modern systems use solid-state dynamic random access memory (DRAM), made in the form of strips with microchips and contacts soldered on them. They can be extracted and exchanged for others, for example, of a larger volume. ROMs are placed directly on the board and can only be replaced for repair purposes. RAM can store up to 64 GB of information in one module, the capacity of one permanent chip is significantly less - a few MB.


RAM Read-only memory
Volatile, cleared when the power is turned offNonvolatile, data retained
Used in computer operations, works with applicationsUsed when system startup, does not interact with applications
Stores data about open documents and running applicationsStores firmware for managing components
Provides fast reading and fast writingWriting is slow
Placed on discrete modules that need to be replacedIntegrated on device motherboard
Can accommodate a large amount of informationA single chip contains several MB of data