Computers are playing a vital role in our lives. They have a lot of parts and functions. So, we need to know about the different parts of the computer. Everyone has heard about these two things i.e, RAM and ROM but most of them don’t know about it. Some of them only know about RAM but they don’t know about ROM. These are two important parts of any computer system. In this post, we are going to tell you about Major Differences between RAM and ROM.

Major Differences between RAM and ROM

  1. RAM stands for Random Access Memory.
  2. RAM is volatile. It means that the data evaporates or disappears when the system is Switched off.
  3. It stores data temporarily.
  4. RAM is both readable and editable. We can change data in RAM.
  5. RAM needs electricity to maintain data.
  6. It is costlier than ROM.
  7. It is fast but uses more power.[/mks_one_half]
  1. ROM stands for Read Only Memory.
  2. ROM is Non-Volatile. It means data do not disappear even if disconnect from the power supply.
  3. It stores data permanently.
  4. ROM is only readable. You cannot edit or change ROM.
  5. It does not need electricity to maintain its data.
  6. It is cheaper than RAM.
  7. ROM is also faster but uses less power than RAM.

Primary or secondary memory

RAM - Difference between RAM and ROM
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The main confusion about RAM and ROM is whether they are the 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 are primary memory and secondary memory. In easy words,

  • Primary memory is the memory which can be directly accessed by CPU. It is also known as primary storage or main storage.
  • Secondary memory is the memory which 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.

Let’s study about RAM and ROM deeply to understand it properly.

What Is RAM

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RAM stands for Random Access Memory. It is a form of computer data storage which 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.

Have you ever used Microsoft paint on your computer? Sometime you might have drawn the wrong line or you have erased your drawing by mistake. Then you might have pressed the shortcut key Ctrl + Z to recover the data. Have you wondered from where the data recovered magically? The data is saved on your RAM temporarily until you close Paint or disconnect the system from the power supply.

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More the programs you open on your system more the RAM you require. Therefore, when you open too many apps or programs your system becomes slow because it runs out of RAM or memory.

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.

Is RAM expandable?

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Yes, 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.

It is difficult to change the RAM of the laptop on your own. But 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.

You can expand your RAM size even to 64GB or more. Normally laptop has 4-8GB RAM which is more than sufficient for normal uses.

Types Of RAM

Basically, there are two types of RAM

  1. Dynamic Random Access Memory (DRAM)
  2. Static Random Access Memory (SRAM)


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DRAM stores each bit of data or program code in a storage cell consisting of a transistor and a capacitor. A DRAM storage cell is dynamic. It means that it needs to be refreshed or given a new electronic charge every few milliseconds to compensate for charge leaks from the capacitor. But it is cheaper than SRAM.

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

DRAM can even be subclassified into other categories. We are not going to that level. If you want to read more you can read it Here.

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It is a type of memory which keeps data in memory as long as power is supplied to the system.  Therefore it is needed to be refreshed periodically. It is much faster than DRAM which makes it more expensive. Consequently, DRAM is more prevalent memory in computer systems.

What is ROM?

ROM stands for Read Only Memory. It is a type of computer storage which stores data permanently of your system. ROM contains the programmes which are necessary for starting any computer. It has data about booting up and input-output services.

We can not change data in ROM because it is Read Only Memory. It contains a program called BIOS. This program is written and saved already by the manufactures when you buy any system. It can not be changed or edited.

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.

When you buy any system and you do not have any Operating System(OS) installed on your drive then if you start your system you can see a screen with some menus or words like “no bootable device, insert disk”. This is the BIOS. When you get an OS, BIOS helps you to install the OS on your system.

Types of ROM

Basically, there are 3 types of ROMs:

  1. Programmable Read Only Memory (PROM)
  2. Erasable and Programmable Read Only Memory (EPROM)
  3. Electrically Erasable and Programmable Read Only Memory (EEPROM)


EEPROM - Difference between RAM and ROM
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It is One Time Programmable (OTP) ROM. The user buys a blank ROM and enters his desired contents using a special device called the PROM programmer. During the process, the circuit fuses or antifuses within the chip. Which makes it usable only once.



By Bill BertramPixel8Photo by:Bill BertramCamera:Fujifilm FinePix F106.3 Megapixels 3x Optical zoom – Own work, CC BY-SA 2.5, Link

Since it is erasable and programmable ROM, it can be erased and be reprogrammed.  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. And again now it will require an even higher voltage to rewrite the EPROM. Repeated reprogramming would lead to wear out of EPROM. It can be reprogrammed about 1000 times.


By © Nevit Dilmen, CC BY-SA 3.0, Link

EEPROM can be programmed and erased electrically. In EEPROM, any location can be selected, erased and programmed. It makes it flexible. But EEPROMs can be erased one byte at a time, rather than erasing the entire chip. Hence, the process of reprogramming is flexible but slow. It can be reprogrammed about 10,000 times which is 10 times more than the EPROM.

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RAM and ROM are the two important parts of a computer system. Most of the people do not know about ROM, its functions and its types. The difference between RAM and ROM is also frequently asked at schools, colleges. And still, students are confused about them.

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