What Is ROM & Its Types?

RAM & ROM are the two major types of computer memory. ROM stands for Read-Only Memory. While RAM stands for Random Access Memory.

Unlike RAM, the Read-Only Memory cannot be directly accessed by the CPU. It plays an important role in the Booting Process. The info is first transferred to the RAM then CPU can access that data from the RAM.

Read-Only Memory may be a non-volatile memory. The info inside the Read-Only Memory retains albeit the facility of the CPU is transitioned.

What is ROM (Read-Only Memory)?

The capacity of ROM is relatively smaller than RAM. It’s slower and cheaper than RAM. The info in Read-Only Memory can only be read by a CPU. That’s why it’s said read-only. The info in Read-Only Memory can’t be modified.

What is ROM

What Does Read-Only Memory Do?

ROM stores “Firmware,” which is everlasting software that’s difficult-stressed out with integrated circuits. The producer suits a specially designed Read-Only Memory chip into a tool.

ROMs forward the instruction that a computer requires during bootstrapping. I feel that you guys must remember the BootStrapping process.

It may be a self-starting process where the essential software is loaded into the pc memory after power on or on a reset.

Unlike the non-unstable reminiscence of hard power, it’s tough and time-eating to rewrite a Read-Only Memory chip’s reminiscence.

In most cases, it’s impossible to adjust included circuits, which may additionally suggest you can’t update more primary forms of Read-Only Memory.

You’ll be capable of reprogramming a few cutting-edge sorts of Read-Only Memory, but best at sluggish speeds and with a special gadget.

These hurdles make traditional Read-Only Memory poorly-proper for capabilities that require frequent characteristic updates or are liable to insects or protection issues.

Read-Only Memory performs like a disk array. It includes a grid of rows and columns that are used to turn the machine on and stale. Each element of the array correlates with a specific memory element on the ROM chip.

A diode is used to attach the corresponding elements. When a request is acquired, the deal with entering is used to discover the specific memory area.

The price that is studied from the ROM chip must fit the contents of the chosen array detail.

Types Of ROM

Basically, Read-Only Memory has the following  three types:

  • P ROM
  • EP ROM 


P ROM stands for Programmable Read-Only Memory. It is often modified on just one occasion by the user. The parent chip has small fuses that are burned open during programming. That’s why it’s not erasable.


EP ROM stands for Erasable And Programmable Read-Only Memory. The content of this Read-Only Memory is often erased using ultraviolet rays.

Therefore the EP Read-Only Memory is often reprogrammed. During programming, an electrical charge is trapped in an insulated gate region.

The charge is often retained for quite 10 years because the charge has no leakage path. For erasing, discharge ultraviolet is skilled a quartz window for about 40 minutes. This exposure to ultraviolet dissipates the charge.


EEP ROM stands Electrically Erasable and Programmable Read-Only Memory. It is often erased electrically and pre-programmed about 10000 times.

Both erasing and programming in EEP Read-Only Memory take about 4 to 10 milliseconds. It is flexible because any location in EEP Read-Only Memory is often selectively erased and programmed.

But just one byte is erased at a time instead of the entire chip. That’s why it’s quite slow.


P Read-Only Memory EP Read-Only Memory EEP Read-Only Memory
Developed by Wen Tsing Chow in 1956 Developed by Dov Frohman in 1971 Devloped by George Perlegos in 1978
It is often modified on just one occasion by the users It is often erased & reused Can be erased & reprogrammed repeated through electrical voltage
Reprogramable only once Can be programmed using UV light Can be reprogrammed using an electrical charge
Example: CD disk Ex: CD(RW)  Example: Pen Drive

Difference Between ROM Aand RAM

So guys! here we have a comparison chart that shows a considerable difference between RAM and ROM

Difference Between RAM Vs ROM


Do You Know About:

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button