Difference Between RAM and ROM & Their Types

Difference Between RAM and ROM & Their Types

RAM, which stands for random access memory, and ROM, which refers to read-only memory, both are the internal memories of the computer. They differ from each other in terms of their storage capacity, physical size, usage, and more. In this article, we’ll discuss about differences between RAM and ROM.

Difference Between RAM and ROM :

RAM (Random Access Memory)

RAM means that CPU can directly access any address and location of RAM memory that is why it is named as Random Access Memory and it is very quickly accessible.

Key Features of RAM

  • RAM is a volatile memory. It stores the data until the power is switched on. Once the power goes off the whole data in RAM gets erased and it only stores data which has to be currently processed.
  • The storage capacity of RAM is high. Ranging from 64 MB to16 GB
  • RAM is the fastest and most expensive memory of the computer. It is very expensive because of its speed.
  • RAM is a read-write memory of the computer. It means that the processor can read the instructions from the RAM and write the outcome into the RAM. In that way the data can be modified in RAM.

Types of RAM

  1. Static RAM

Static RAM is one that requires the constant flow of the power to store the data in it. Here interrupted power can lead to data loss. The Static RAM is created by transistors and latches. It is much faster and costlier than Dynamic RAM. It is mainly used as computer cache memory.

  1. Dynamic RAM

Dynamic RAM needs to be refreshed to retain the data it holds because capacitors are used in the construction of Dynamic RAM. The capacitor has a property of charge leakage. Therefore, Dynamic RAM requires a separate refresh circuit. It is slower and economical than Static RAM and it is highly dense.

ROM (Read Only Memory)

Unlike RAM, the ROM memory can’t be directly accessed by CPU. The data is first transferred to the RAM and then CPU can access that data from the RAM.

Key Features of ROM

  • ROM is a non-volatile memory. The data inside the ROM retains even if the CPU power is turned off.
  • ROM capacity is relatively small than RAM.
  • It is cheaper and slower than RAM.
  • The data in the ROM can only be read by the CPU, which is why it is said read-only memory. The data in ROM cannot be modified.
  • ROM stores and keeps the instruction that computer requires during Bootstrapping. Bootstrapping process is a self-starting process where the basic software’s are loaded into the computer memory after power on or on a reset.

Types of ROM

  1. PROM

Programmable ROM can be modified only once by the user. The PROM chips have small fuses which are burned open during programming which is why it is not erasable.

  1. EPROM

Erasable and Programmable ROM, the data of this ROM can be erased using ultraviolet rays and the ROM can be reprogrammed and reused. During programming an electrical charge is retained in an insulated gate region. The charge can be trapped for more than ten years since the charge has no leakage path. For erasing discharge, ultraviolet light is passed through a quartz crystal window for about 40 minutes. This exposure to ultraviolet light dissipates the charge.


Electrically Erasable and Programmable ROM, it can be erased electrically and pre-programmed about ten thousand times. Both erasing and programming in EEPROM takes about 4 to 10 milliseconds. It is flexible because any location in EEPROM can be selectively erased and programmed but only one byte is erased at a time rather than entire chip that’s why it is kind of slow.


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