Difference between RAM and 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 a hardware element where the data being currently used is stored. It is a volatile memory. Types of RAM:
- Static RAM, or (SRAM) which stores a bit of data using the state of a six transistor memory cell.
- 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:
- Programmable ROM, where the data is written after the memory chip has been created. It is non-volatile.
- Erasable Programmable ROM, where the data on this non-volatile memory chip can be erased by exposing it to high-intensity UV light.
- Electrically Erasable Programmable ROM, where the data on this non-volatile memory chip can be electrically erased using field electron emission.
- Mask ROM, in which the data is written during the manufacturing of the memory chip.
The following table differentiates ROM and RAM:
|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, with respect to ROM||Small size with less capacity, with respect to RAM|
|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.|
|Chip Size||A RAM chip can store only a few gigabytes (GB) of data.||A ROM chip can store multiple megabytes (MB) of data.|