We explain what ROM memory is and what this type of storage is for.Also, the types of ROM and what is RAM.
What is ROM memory?
In computing, when we talk about ROM memory (acronym forRead–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, it can be recovered but not modified or intervened.
ROM memory is sequential access and its presence is independent of the presence of a power source. As has been said, its content cannot be modified, or at least not in a simple and daily way, and it usually contains information entered into the system by the manufacturer, basic, operational, or primary.
This type of memory also operates much slower than its counterpart, RAM (acronym forRandom AccessMemory, that is, Random Access Memory), so its content is usually dumped in 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, despite the fact that their operation is governed by the same traditional rules. However, as their reprogramming process is infrequent and relatively slow, they continue to be called in the same way.
What is ROM for?
ROM has two main uses, which are:
- Software storage. Commonly, computers in the 1980s brought all of their operating system stored in ROM, so that users could not accidentally alter it and interrupt the operation of the machine. It is still used today to install the software boot or more basic operation (BIOS, SETUP and POST, for example).
- Data storage. Since users often do not have access to a system ROM, it is used to store the ROM of a system. data that will not require any modification in the life of the product, such as look-up tables, mathematical or logical operators and other information of a technical nature.
ROM memory types
Let's consider three different types of ROM memory:
- PROM. Acronym forProgrammable Read–Only Memory (Programmable Read Only Memory), is of the digital type and can be programmed only once, since each memory unit depends on a fuse that burns when doing so.
- EPROM. Acronym forErasable Programmable Read–Only Memory (Erasable Programmable Read Only Memory) is a form of PROM memory that can be erased when exposed to ultraviolet light or high levels of voltage, erasing the information contained and allowing its replacement.
- EEPROM. Acronym forElectrically Erasable Programmable Read-Only Memory (Electrically Erasable and Programmable Read Only Memory) is a variant of EPROM that does not require ultraviolet rays and can be reprogrammed in the circuit itself, allowing access to the bits of information individually and not together.
RAM
Unlike ROM, RAM is much faster and freely writable. This means that all running programs go to this memory bank, but strictly temporarily: when shutting down or restarting the system, the entire RAM memory is cleaned. This does not mean, of course, that the information saved on disk is lost, but only that in execution.
RAM memory today is extremely efficient, fast and inexpensive, which is why many systems engineers prefer to make use of it instead of ROM.