Computer Organization | RAM vs ROM



Prerequisite – Types of computer memory (RAM and ROM)
Random Access Memory (RAM) is used to store the programs and data being used by the CPU in real time. The data on the random access memory can be read, written, and erased any number of times. RAM is the hardware element where the data being currently used is stored. It is a volatile memory. Types of RAM:

  1. Static RAM, or (SRAM) which stores a bit of data using the state of a six transistor memory cell.
  2. Dynamic RAM, or (DRAM) which stores a bit data using a pair of transistor and capacitor which constitute a DRAM memory cell.

Read Only Memory (ROM) is a type of memory where the data has been prerecorded. Data stored in ROM is retained even after the computer is turned off ie, non-volatile. Types of ROM:

  1. Programmable ROM, where the data is written after the memory chip has been created. It is non-volatile.
  2. Erasable Programmable ROM, where the data on this non-volatile memory chip can be erased by exposing it to high-intensity UV light.
  3. Electrically Erasable Programmable ROM, where the data on this non-volatile memory chip can be electrically erased using field electron emission.
  4. Mask ROM, in which the data is written during the manufacturing of the memory chip.

The following table differentiates ROM and RAM:

Difference RAM ROM
Data retention RAM is a volatile memory which could store the data as long as the power is supplied. ROM is a non-volatile memory which could retain the data even when power is turned off.
Working type Data stored in RAM can be retrieved and altered. Data stored in ROM can only be read.
Use Used to store the data that has to be currently processed by CPU temporarily. It stores the instructions required during bootstrap of the computer.
Speed It is a high-speed memory. It is much slower than the RAM.
CPU Interaction The CPU can access the data stored on it. The CPU can not access the data stored on it unless the data is stored in RAM.
Size and Capacity Large size with higher capacity. Small size with less capacity.
Used as/in CPU Cache, Primary memory. Firmware, Micro-controllers
Accessibility The data stored is easily accessible The data stored is not as easily accessible as in RAM
Cost Costlier cheaper than RAM.


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