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Prerita Agarwal
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23 Jul, 2024 @ 01:30 PM


Can you imagine your life where you forgot how to walk or how to breathe after waking up from a good nights' sleep or where you just forgot what you did just a second ago? No, right? So, RAM (Random Access Memory) is the part of your brain that keeps track of what you did just a second ago, and ROM is the part of your brain that reminds you every morning how to walk and perform the fundamental daily tasks. That was just about the gist of it. Let's dive deeper into the topic.

Computer memory is of two types- Primary Memory (RAM and ROM) and Secondary Memory (Hard disk, pen drive, etc.). You can refer to the below diagram for a better understanding.

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RAM stands for Random Access Memory. It is a primary volatile memory and stores the data required by the CPU while executing a program. RAM is volatile memory meaning that the data is lost when the power is turned off. The data stored in RAM can be read and changed in any order. RAM can further be classified into SRAM (Static Random Access Memory) and DRAM (Dynamic Random Access Memory).


As suggested by the word static, Static-RAM holds the data as long as power is available. It uses latching circuitry (D Flip-Flops) to store every bit. It can store only a limited number of bits per chip, making it more expensive. SRAM is faster than DRAM, but it uses more power and generates more heat. SRAM is used in cache memory and CPU internal registers.


Dynamic-RAM requires a recharge every few milliseconds to maintain its data, hence the name dynamic. It stores each bit of data in a memory cell consisting of a capacitor and a transistor, based on MOS (Metal Oxide Semiconductor) technology. Due to this, it can store many bits per chip, making it inexpensive. It uses less power than SRAM and generates less heat. It is primarily used in main memory. The RAM in computers or the graphics memory on the graphics card, which we usually refer to, is DRAM.

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ROM stands for Read-Only Memory. As the name implies, the contents stored on this memory can only be read and usually can not be changed. However, there are some types of ROM where modification is allowed. The manufacturer programs the ROM, after which the data and instructions can't be altered or modified. ROM is a non-volatile memory; therefore, it retains the data stored in it even after a power cut. It holds the crucial information essential to operate the system. For example- a program that is needed to boot the computer. It is used where the programming needs not to be changed like embedded systems, calculators, etc. ROM can further be classified into four types: PROM (Programmable ROM), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), and MROM (Mask ROM).

PROM (Programmable ROM)

PROM is a type of ROM where the user can program the ROM but only once in its lifetime. After it has been programmed, the data and instructions can't be changed by anyone.

Uses: Cell Phones and Video Game Consoles

EPROM (Erasable Programmable ROM)

EPROM can be programmed by the user more than once, unlike PROM, but to do so, the user needs to erase the previous data and instructions stored on it by exposing it to Ultraviolet light.

Uses: Intel 8048 micro-controller (to store programs)

EEPROM (Electrically Erasable Programmable ROM)

EEPROM can also be reprogrammed multiple times. But here, it is erased and reprogrammed electrically without using Ultraviolet lights. It is also known as Flash EEPROM as it is similar to flash memory. It can be erased and reprogrammed continuously, up to 10000 times.

Uses: Computer (to store BIOS)

MROM (Masked ROM)

MROM chips are made of ICs (Integrated Circuits). It is programmed during the manufacturing process only and can't be reprogrammed later. However, if reprogramming is required, the process would be complex or slow.

Uses: It is the oldest type of ROM, and it's not used anywhere in today's world.

Read About - Shift Registers in Digital Electronics

Differences between RAM and ROM

You can also read about the memory hierarchy Demultiplexer


  1. Is a hard disk a type of ROM?
    No, hard disk is a type of secondary memory, and ROM is primary memory.
  2. Which is the fastest memory?
    Cache memory is the fastest.
  3. Which memory is volatile?
    RAM is a volatile memory.
  4. Which memory is used primarily in the startup process of a computer?
    ROM is used in the booting process of a computer.
  5. Among RAM and HDD/SDD, which one is faster?
    RAM is faster than HDD and SDD.

Key Takeaways

In this article, we have learned what RAM is and what ROM is. We also discussed different types of RAMs and ROMs and their real-life applications. I hope you have learned something from this article. Don't stop here; learn about the evolution of computers and the classification of computers to further increase your knowledge in Computer Architecture and Organization.

Recommended Reading: 

Clean Architecture

Learn more, Difference Between List and Set

Happy Learning Ninja :) 

Topics covered
PROM (Programmable ROM)
EPROM (Erasable Programmable ROM)
EEPROM (Electrically Erasable Programmable ROM)
MROM (Masked ROM)
Differences between RAM and ROM
Key Takeaways