ROM MEMORY  ▷ What is it and what is it for? Rates ▷ 2020

ROM memory is an essential part of our devices. Many people, many, use it without even knowing that it exists, but its work is undoubtedly invaluable in the world of technology.

We can anticipate that it is about a type of memory that is used to boot our systems and, with it, the devices, whether big or small. This comes from the factory and cannot be tampered with.

For the rest, we encourage you to know in depth what it is, the types there are, how our devices use it and how it differs from the, already somewhat more known, RAM memory.

What is and what is the ROM memory of a computer for?

What is how ROM works

ROM is part of the hardware of devices, whether they are computers, phones, tablets … and is related to their startup process and their maintenance and their usability capabilities.


To define this concept, we will first go to your name, ROM, which is an acronym for Read-Only Memory, or read-only memory.

The main feature of this piece of software that we have already seen that it does not stop being a memory, it is, at first, unalterable (Later we will see that there are ways to modify them, but it is not easy to do so, and less at the user level).

So, we have to ROM is a memory without the ability to be written, inadequate to be modified. This is due, in large part, in addition to the logical accidents that a user could cause due to ignorance, the fact that include inside the firmware of certain hardware, that is, a specific application to control and carry out tasks.

Another essential feature is that it does not require a power supply, so that storage is permanent. ROM it is made up of a set of fairly basic programs that the system in question read when turned on. These are provided by the manufacturer when mounting the chip. Physically, the ROM is on a small chip which does not include anything else.

Functions on PC and mobile devices

ROM works as both a data store and a software store. More specifically, what it saves is a compendium of codes and starting instructions, including language interpreters, OS programs, control programs, information tables …

It will also serve for hardware operation check who accompanies and to help the operating system be recognized what moves the system and peripherals input and output.

Let’s see how it does it in each situation:

  • BIOS: To work with the BIOS, which is a program that controls the essential input-output interfaces, we have the BIO ROM, a card on the motherboard that is read-only. The BIOS is saved in ROM because it is necessary to read the rest of the memory elements of any computer, so we cannot store it in any of them.
  • Bootstrap: It uses the disk and also the floppy disk drive to run the operating system by loading and executing random access memory. This occurs if there are defects in the hard disk system.
  • CMOS configuration: It allows access to a screen that appears when the equipment is turned on and that allows the modification of certain system parameters.
  • POST Power On Self Test: It is a bootable autorun software that seeks to test the system.
  • Back: It is the copying of instructions from the ROM in the RAM to have them more quickly.
  • Data storage: It only makes sense to save in them those that should not be modified while the device is useful, such as a look-up table.

ROM or read-only memory types and examples

Having some contact with the computer and having read the above, you can already imagine that, indeed, there are different types of ROMs, considering that it is programmable, read-only or erasable in one way or another, including, even, subtypes.

ROM memory types

The basis of this classification is semiconduction:

ROM or read-only memory

Make a storage of information without electrical current. It is also known as non-volatile memory because it is not lost when the system is turned off.

PROM, OTP, or programmable read-only memory

Is that which requires the use of a programming device called PROM to be written. It works at high voltage with the intention of create and destroy internal links on a chip, which is why only a single schedule can be given.

EPROM or erasable programmable read-only memory

This memory is programmable read-only but can also be erased. This is achieved when exposing it to UV light for periods of time greater than 10 minutes. After that, can be rewritten with a high voltage process (even more than what is used to being needed). A cover is used to avoid erasure. We have the handicap of degradation, because the greater the UV exposure, the more wear and tear, being the common thing to have about 1000 reprogramming cycles.

EEPROM or electrically erasable programmable read-only memory

Its base is a semiconductor structure as the previous type, with the exception that the content or part of it is erased with electricity, in the same way that it is rewritten later. This implies that it is not necessary to remove the memory from the computer, although we do have to say that, compared to other memory jobs, it is a slower process.

In turn, we find these subtypes:

  • EAROM or electrically alterable read-only memory: This is modified one bit at a time in a rather slow writing process that requires the use of a high voltage of at least 12 volts. Its use occurs in infrequent partial writing apps and, sometimes, to store in a non-volatile way in order to obtain configuration data of the critical system of the equipment where it is located
  • Flash, Flash ROM or Flash EEPROM: The erasure and rewriting occurs in a faster way and its resistance is very high, being able to offer more than a million cycles. It has replaced old ROMs in many cases.

It is essential to indicate that, to this day, The term ROM is used to refer interchangeably to any type of Read-Only MemoryWell, in fact, the original type is already in disuse due to the improvements that have been implemented to conform the different types that we have been seeing.

ROM and storage memory the same?

Absolutely, it’s funny how ROM has been used erroneously to talk about storage memory of the devices, the one we use to download video games, movies, etc.

So much so that even in stores and on the devices themselves of certain brands (phones and tablets mainly) it is called like that, and we see it in the phone settings and in the descriptions that the “experts” make in their stores to show you the new fashionable phone or a super computer.


  • The ROM we have already seen that it is a tiny memory that has the basics to run the apparatus, a spark so to speak.
  • Is unalterable (in principle) by the user.
  • It is located inside the computer, in the form of a chip.

Storage memory

  • The storage memory is another type of memory, much larger today, which is where is everything that we are saving going to stop in the computer.
  • We have full access to this content; We can consult it whenever we want and it can also be deleted at will, using the space to save new information when we need it. The things that are saved in the storage memory are not essential or critical for the operation of the device, is all that content that we download and install voluntarily and that we want them to remain a posteriori.
  • The hardware that hosts the storage memory is called HDD, and can be both internal, as part of the equipment, or an add-on, an external hard drive, which would be a hybrid storage peripheral. It is also considered a memory of storage the pen drive, although the capacity is less, but it works the same.

Main differences between ROM and RAM

Differences between ROM and RAM

Easily confused by those who only make superficial use of computers and other devices, both concepts refer to memory systems of a device or equipment but they are not the same at all. You can see more in depth all the differences between RAM and ROM from here.


  • We have already seen that it is the memory of only reading, that is, a compendium of information that is only useful to read and, with it, start and maintain the correct operation of the equipment in question.
  • It is basic startup, configuration and maintenance information, non-volatile, clustered on a small chip.
  • Work with essential information, required to boot the system.


  • The RAM is the acronym for Random Access Memory or random access memory.
  • This means that access is given to any existing memory byte in our system without the need for access to the preceding bytes.
  • This is erasable, volatile, perishable, it is lost, I eat very late, when it stops receiving energy from a current source. It also happens to be faster. Its physical format is a larger board with complex circuits.
  • Works with secondary software that requires a temporary effort such as video games, browsers, etc.

If you have any questions, leave them in the comments, we will answer you as soon as possible, and it will surely be of great help to more members of the community. Thank you! 😉

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