What Is Read-Only Memory (ROM)?

Understanding memory is crucial in the world of computers and electronics. It is the foundation for storing and accessing data. It allows devices to process information and function as intended. One of the key components of memory is Read-Only Memory (ROM). In this article, we’ll explore the nature of ROM, its characteristics, and its importance in the technological landscape.

What is ROM?

Read-only memory, or ROM for short, is a computer memory that stores data permanently on electronic devices. ROM is a non-volatile memory, which means that it can store information securely and persistently even if the power is switched off.

What are the basic characteristics of ROM?

ROM has key characteristics that make it an essential part of any electronic device. These include:

  • Non-volatile:

ROMs are non-volatile computer memory, which means they can retain their data even if there’s no power supply. This is helpful for storing critical programs and instructions that a device needs to function so it knows what to do the next time it’s powered on.

  • Persistent:

Another characteristic of ROM is being able to persistently store information even if the device’s power is off. This “persistence” is crucial to ensure essential instructions, like the core programs needed for a device to boot up, are always readily available.

  • Read-only:

As the name suggests, data stored in ROM is read-only. This means it can only be accessed and used by the device and not modified by users during normal operation. This limitation is critical for the stability, security, and reliability of embedded systems.

What data does ROM store?

ROM stores data essential for a device’s function and operation. Here are some types of data that can be found in ROM:

  • Firmware:

Firmware is software that provides control, monitoring, and data manipulation of engineered products and systems. It controls low-level hardware functions and the boot process.

  • BIOS (Basic Input/Output System):

A BIOS is a type of firmware that executes initial hardware diagnostics. It also loads the operating system.

  • Bootloaders: 

Bootloaders are small programs that initiate the startup process and load the operating system into RAM.

  • Microcode: 

Microcodes are low-level instructions controlling certain processors’ functionality, which is essential for defining fundamental operations.


As mentioned, ROM, or Read-Only Memory, is a non-volatile computer memory. Data stored in ROM is permanent and persistent, meaning it is not erased even if the device’s power is off.

In contrast, RAM, or Random Access Memory, is a volatile computer memory. This means that the data stored in RAM is erased once the device is turned off. RAM acts as a computer’s temporary workspace, allowing programs and data to be loaded quickly for processing by the CPU. Some data stored in RAM are operating systems, cached data, active files, and running applications.

ROM’s role in a computer system

Read-only memory or ROM is a computer memory where data is stored permanently and can only be accessed for reading, providing the foundational instructions for the system to function. ROM plays a crucial role in a computer system’s stability, security, and reliability. Stability by preventing accidental modifications or software errors from corrupting the boot process or other critical functions, security by storing critical code like the BIOS and bootloaders in ROM to ensure protection from malware attacks, and reliability by ensuring the system has a trustworthy source of code to execute at startup.

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