11 Actual Difference Between RAM and ROM

What is the difference between RAM and ROM?“. It is one of the most asked questions asked by computer students. It is asked in exams from classes 7th to higher education, in GK questions to Competitive exams. Still, most people are confused about it. Given below are the major differences between RAM and ROM in tabular form.

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Difference between RAM and ROM in tabular form?

The difference between RAM and ROM is according to their classification. The following are the differences in points.

Full-Form RAM stands for Random Access Memory. ROM stands for Read-Only Memory
Function It stores all the data to run your applications and software. It stores only the data necessary for booting your system.
Volatility RAM is volatile. It means that the data will evaporate or disappear when you shut down the system. ROM is Non-Volatile. It means data do not disappear even if disconnect from the power supply.
Data Storage It stores data temporarily. It stores data permanently.
Modifications RAM is both readable and editable. We can change data in RAM. ROM is only readable. You can’t edit or change data in ROM.
Maintenance RAM needs electricity to maintain data. It does not need electricity to maintain its data.
Cost It is costlier than ROM. It is cheaper than RAM.
Speed It is fast but uses more power. ROM is also faster but uses less power than RAM.
Type Static-RAM(SRAM) and Dynamic-RAM(DRAM) PROM, EPROM, and EEPROM
Storage Capacity Storage capacity can vary from 1 GB to 256GB. Newer versions are coming with more capacity. It requires less storage. Normally it is 4 MB to 8 MB only.
Physical Size Desktop RAM is 5-6 inches long and 1 inch wide. Laptop RAM is 2.5-3.5 inches long and 1 inch wide. ROM size is different for different devices. It can be smaller than an inch or bigger than that.

Explanation of the differences:

Given below are the descriptions of the differences on each point.


Difference between RAM and ROM

  • RAM stands for Random Access Memory.
  • It is a form of computer data storage that stores current data of the computer.
  • If you are running multiple programs on your system then you’re gonna need more RAM. It saves your data temporarily. Let’s make it more clear.

Different types of programs occupy a different amount of RAM. If you have 3GB or 4GB RAM then you might observe the slowness of your computer when you run two heavy programs like Photoshop, Corel Draw together. But if you have more RAM then you can easily operate not only 2 programs but 4-5 programs also.


  • ROM stands for Read-Only Memory.
  • It is a type of computer storage that stores data permanently from your system. ROM contains the programs which are necessary for starting any computer.
  • It has data about booting up and input-output services.
  • It contains a program called BIOS. This program is written and saved already by the manufactures when you buy any system. You cannot change or edit it.

BIOS stands for Basic Input/Output System. It handles all basic input and output services. BIOS loads the OS from the hard drive. It is the first software run by your system when you turn it on. It also handles power management.

Primary or secondary memory?

The main confusion about the difference between RAM and ROM is whether they are part of primary memory or secondary memory. Some website says that RAM is primary and ROM is secondary. And says both are primary. Then Which one is true?

First Let’s understand what is the difference between primary memory and secondary memory. In easy words,

  • Primary memory is the memory that can be directly accessed by CPU. It is also known as primary storage or main storage.
  • Secondary memory is the memory that can not be directly accessed by CPU. These are first accessed by RAM and then by the processor.

Since both RAM and ROM can be directly accessed by CPU then both are the part of the primary memory. Flash drives and hard drives are some examples of secondary memory because they are firstly accessed by RAM, not by the processor.


RAM stores your temporary data while you are using your system like recent tabs, history, recent commands etc. Whereas, ROM does not store your personal data. It stores some pre-written programs by the manufacturer of the system. It is used to install an operating system. The screen you see before installing OS is the BIOS, stored in ROM.


RAM is volatile in nature. It means as soon as you shut down the system, the data stored in RAM evaporates. It will store your data only until you keep the system on. Unlike RAM, ROM is not volatile. It does not lose its data even if you remove the power supply from the system. It will store your data forever.

Data Storage

Since RAM is volatile in nature, it can not hold data for long. It stores data temporarily. It stores data until the system is connected to power. Each time you shut down the system and start it again, the data stored in RAM is removed. Whereas, ROM stores permanently. You can not delete the data from ROM (Its data may be removed with some sophisticated methods).


You can easily modify the data stored in RAM. RAM is readable as well as editable. On the other hand, You can not edit or modify the data stored in ROM. ROM is only readable. Even you use those complex methods to change data in ROM, you can only remove all data from it at once. You can not modify its existing data.


RAM only needs a power supply to store its data while ROM does not need anything to maintain its data.


RAM is costlier than ROM because of many reasons. RAM involves more complex technology to store its data than the ROM.

Although ROM stores all the necessary data to run a system, it does not require much space while RAM needs more storage than ROM. Therefore, it increases prices.


Some types of ROMs are very faster than some older types of RAM. But if you see an overall result then the RAM is the winner. Data stored in RAM can be read instantly while ROM is a little bit slow. You might not be able to measure the difference but it exists there.

Also, the writing speed of RAM is also fast whereas the writing speed of ROM is very slow as it requires complex methods to write.

Storage capacity

ROM requires less space because as we discussed earlier that it does not store our personal data. It stores the BIOS for the system which occupies very little space. Hence the storage capacity of ROM is less for a normal system. It may require more storage according to the type of computer.

Whereas RAM stores our current data as well as perform some other tasks, it requires much more storage capacity. Its storage can be up to 256GB and even more for the latest RAM.

Can we increase the storage capacity of RAM and ROM?


  • There is no need to increase or decrease the storage capacity of ROM because it is the work of the manufacturer to decide the storage capacity for the ROM. They already design sufficient storage for the ROM.

RAM is expandable.

  • If you are running out of RAM then you can expand it. You can expand your system’s RAM at home if you are having a computer but you might need to visit a help center to expand the memory if you are having a laptop.
  • On Computers, there are separate dedicated RAM slots where you can easily fit a new RAM. Just buy any RAM from your nearby shops or purchase online. Put it in RAM slots of CPU. It is super easy.

Physical Size

Desktop RAM is 5-6 inches long and 1-inch wide and Laptop RAM is 2.5-3.5 inches long and 1-inch wide. The size of ROM is normally 1-inch wide and half of the length of the RAM.

Physical size does not matter much for any system. Earlier, the size was too large but with the advancement in the technology their size is reducing. The size may even reduce further with better technology.


There are two types of RAM

Types of RAM


Dynamic Random Access Memory (DRAM)

  • It loses its data in a very short time even when the power supply is on. Therefore it is refreshed thousands of times in a second automatically.

Static Random Access Memory (SRAM)

  • It is a type of memory that keeps data in memory as long as power is supplied to the system which makes it faster.

There are three types of ROM :

Types of ROM

Programmable Read-Only Memory (PROM)

  • It is a One Time Programmable (OTP) ROM.
  • During the writing process, the circuit fuses or anti-fuses within the chip. Which makes it usable only once.

Erasable and Programmable Read-Only Memory (EPROM)

  • EPROM can be erased by exposing it to ultraviolet rays for about 40 minutes.
  • While rewriting EPROM, higher voltage is required than usual. It can be erased again with the same method for 1000 times.

Electrically Erasable and Programmable Read-Only Memory (EEPROM)

  • EEPROM can be programmed and erased electrically. The process of reprogramming flexible but slow.
  • It can be reprogrammed about 10,000 times which is 10 times more than the EPROM.

Difference between RAM and ROM pdf

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Requested questions

Q.1) Why ROM is slower than RAM? – Asked by Sunny Kumar Saini

Ans. Actually, ROM is not slow. Making of ROM is slower than RAM. There is no comparison between RAM and ROM because both have different speeds according to their functions.

Q.2) Why RAM and ROM are not suitable to store our work data, why do we need additional storage devices for it? – Asked by Vishal Kumar

Ans: To answer this question, first, you have to know what are RAM and ROM?

  • RAM is a Random access memory. It stores temporary files and data into the system. Once the system is disconnected from the power supply, its data disappear. So you can not store your data in it.
  • Now, ROM is Read-only Memory. There are some prewritten programs called (BIOS) in it. You can not add your data to it. Because ROMs are uneditable. You can not edit them. (Some can be but you need to perform some sophisticated methods).
  • So, please read the post again for a more elaborate answer.

Q.3) Which is more important ROM or ROM? – Asked by Ashutosh Kumar chaurasia

Ans. RAM as well as ROM, are equally important because A system cannot start without these two things. Read our post above completely to know the functions of RAM and ROM. Although one may be expensive and fast. But, both are equally important.

Do You Have Any related questions? Let us know in the comment section.