RAM vs ROM – What Differentiates These Two Terms ?


There are terms in the computer world that can be confusing and sometimes misused. Some people use the terms ROM (read-only memory) and RAM (random access memory) interchangeably.

This is, of course, inappropriate! So I want to open a discussion about the differences between RAM and ROM. I would appreciate your opinions on this also.

RAM and ROM are both types of computer memory. RAM is used to store computer programs and data that the processor needs in real time. Data in RAM is unstable and is erased when the computer is turned off. ROM contains pre-recorded data and is used to boot the computer. ROM data is static and remains in the computer even if it is turned off.

R.A.M (Random Access Memory)

RAM is the largest piece of memory that exists in computer hardware. RAM is used to store programs and data used by the central processor in real time.

Data in random access memory can be read, written, and erased any number of times.

It is volatile memory, which means that the data stored in RAM evaporates as soon as you turn off the power.

This is one reason why random-access memory cannot be used as permanent storage, even though it is much faster than traditional hard drives based on magnetic disks.

Types of RAM:

  • Static RAM.
  • Dynamic RAM.

SRAM (Static RAM):It stores bits of data using the state of a six-transistor memory cell. SRAM is much faster than DRAM, but costs more.

DRAM (Dynamic RAM):It stores bit data using a pair of transistor and capacitor that make up a DRAM memory cell.

R.O.M (Read-Only Memory)

Another prominent type of memory present in a computer is ROM. As the name implies, the data in this memory can only be read by the computer. So, what is the reason for using these read-only memory chips when we have RAM chips?

ROM is a non-volatile memory, it does not forget data even when the power is turned off. ROMs are used to store firmware for hardware that receives almost no regular updates, such as BIOS.

Data in traditional ROM form is hardwired to it, i.e., written at the time of manufacture. Over time, read-only memory has been developed that supports erasing and overwriting data, although it cannot reach the level of efficiency of random access memory.

Types of ROM:

  • Mask ROM.
  • PROM.
  • EPROM.

Mask ROM: This is the type of ROM for which the data is written during the manufacturing of the memory chip.

PROM (Programmable Read-only Memory): The data is written after the memory chip has been created. It is non-volatile.

EPROM (Erasable Programmable Read-only Memory): The data on this non-volatile memory chip can be erased by exposing it to high-intensity UV light.

EEPROM (Electrically Erasable Programmable Read-only Memory): The data on this non-volatile memory chip can be electrically erased using field electron emission (Fowler–Nordheim tunneling). Modern EEPROMs are quite efficient in terms of the read-write capabilities.

The above listed are semi conductor based ROM;

Others like CD-ROM which is an optical storage media is also a ROM

A CD-ROM: is a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs, i.e. it is a type of read-only memory.

10 Key Differences

1. RAM is random access memory and cannot store data without power, while ROM is read-only memory and can store data even without power.

2. RAM is a power-dependent medium for storing information, while ROM is a non-volatile medium for storing data.

3, RAM is much faster and easier to write data to, while ROM is much slower to write data to than RAM.

4. RAM comes in two varieties, that is, static RAM and dynamic RAM, while ROM has three varieties: Mask ROM, PROM, EPROM and EEPROM.

5. Data in RAM is accessed, read, and erased repeatedly, while in ROM, writing data is a relatively very slow process.

6. RAM is used in primary DRAM and SRAM processor cache memory, while ROM is used in BIOS, microcontrollers and other electronic devices.

7. RAM is expensive and not cheap, while ROM is much cheaper compared to DRAM.

8. RAM is large in size and large in capacity, while ROM is smaller in size and even smaller in capacity.

9. RAM is a high-speed memory with read-write operations that occur at a fast pace, while ROM is a slower memory that is less subject to modification and can be done by an external program.

10. In RAM, data can be changed many times, which explains its wide possibilities, while in ROM the data is constant, although it can be changed, but at a very low speed and a limited number of times.

Comparison Table

Comparison RAM ROM
Data RAM data is volatile. Data is present till power supply is present.

RAM data can be read, erased or modified.

ROM data is permanent. Data remains even after power supply is not present.

ROM data is read only.

Storage RAM is a temporary medium of storage.

RAM memory is large and high capacity.

ROM is a permanent medium of storage.

ROM is generally small and of low capacity.

Cost RAM is costly. ROM is cheap.
Function RAM chip is used in the normal operation of a computer. ROM is primarily used in the startup process of a computer or bootstrapping.
Operation RAM is used as CPU Cache, Primary Memory.

CPU can access data stored on RAM.

ROM is used as firmware by microcontrollers.

Data to be copied from ROM to RAM so that CPU can access its data.



Difference between RAM and ROM (tutorialspoint.com)

Answer ( 1 )

    This answer was edited.

    There is one major difference between a read-only memory (ROM) and a random-access memory (RAM) chip: ROM can hold data without power and RAM cannot. Essentially, ROM is meant for permanent storage, and RAM is for temporary storage.

    Alternate explanation

    A ROM chip is a non-volatile storage medium, which means it does not require a constant source of power to retain the information stored on it. By contrast, a RAM chip is volatile, which means it loses any information it is holding when the power is turned off.

    Other differences between a ROM and a RAM

    • A ROM chip is used primarily in the start up process of a computer, whereas a RAM chip is used in the normal operations of a computer once the operating system has been loaded.
    • Writing data to a ROM chip is a much slower process than writing it to a RAM chip.
    • A RAM chip can store multiple gigabytes (GB) of data, ranging from 1 GB to 256 GB per chip. A ROM chip stores several megabytes (MB) of data, typically 4 MB or 8 MB per chip.

    Computer ROM

    A good example of ROM is the computer BIOS, a PROM chip that stores the programming needed to begin the initial computer start up process. Using a non-volatile storage medium is the only way to begin the start up process for computers and other devices. ROM chips are also used in gaming system cartridges, like the original Nintendo, Gameboy, Sega Genesis, and a number of others.


    The oldest ROM-type storage medium can be dated back to 1932 with drum memory. ROM-type storage is still used and continues to be improved upon for better performance and storage capacity.

    Computer RAM

    RAM chips are also used in computers, as well as other devices, to store information and run programs. RAM is one of the fastest types of memory in your computer and can switch quickly between tasks. For example, the Internet browser you are using to read this page has been loaded into RAM and is running from it.

    512 MB memory module

Leave an answer