What is ROM memory?

We explain what ROM is and what this type of storage is for. In addition, the types of ROM and what is RAM.

1. What is ROM memory?

In computer science , when we talk about ROM (acronym for  Read – Only Memory , that is, Read Only Memory ), we refer to a type of storage used in computers and other electronic devices , which is characterized by being only accessible for reading and never for writing, that is, that it can be recovered but not modified or intervened.

The ROM is sequential access and its presence is independent of the presence of a power source. As mentioned, its content cannot be modified , or at least not simply and daily, and usually contains information entered into the system by the manufacturer, basic, operational or primary.

In addition, this type of memory operates much more slowly than its counterpart, RAM (acronym for  Random  Access Memory , that is, Random Access  Memory ), so its content tends to turn to the latter to run faster.

There are, however, versions of ROM memory (known as EPROM and Flash EEPROM) that can be programmed and reprogrammed several times , even though their operation is governed by the same rules of the traditional one. However, as their reprogramming process is rare and relatively slow, they are still called in the same way.

2. What is ROM memory for?

ROM has two main uses, which are:

• Storage software . Commonly, computers in the 1980s brought their entire operating system stored in ROM, so that users could not alter it by mistake and interrupt the operation of the machine. Even today it is used to install the most basic boot or operating software (the BIOS, SETUP and POST, for example).
• Data storage . Since users do not usually have access to the ROM of a system, it is used to store data that will not require any modification in the life of the product, such as query tables, mathematical or logical operators and other technical information.

3. ROM memory types

Consider three different types of ROM memory:

• PROM . Acronym for  Programmable Read – Only Memory  , it is digital and can be programmed only once, since each memory unit depends on a fuse that burns when done.  
• EPROM . Acronym for  Erasable Programmable Read – Only Memory  is a form of PROM memory that can be erased when exposed to ultraviolet light or high voltage levels , erasing the information contained and allowing its replacement.   
• EEPROM . Acronym for  Electrically Erasable Programmable Read-Only Memory  is a variant of the EPROM that does not require ultraviolet rays and can be reprogrammed in the circuit itself, being able to access the information bits individually and not in set.    

4. RAM

Unlike ROM, RAM is much faster and freely writable. This means that all running programs go to this memory bank , but in a strictly temporary way: when the system is turned off or restarted, all of the RAM is cleaned. This does not mean, of course, that the information stored on disk is lost, but only that in progress.

RAM is nowadays extremely efficient, fast and economical , so many systems engineers prefer to use it instead of ROM.