Question

why is Rom called non volatile memory

Answer 1

Non-volatile memory, nonvolatile memory, NVM or non-volatile storage is a type of computer memory that can retrieve stored information even after having been power cycled (turned off and back on). Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer storage devices (e.g. hard disk drives, floppy disks, and magnetic tape), optical discs, and early computer storage methods such as paper tape and punched cards.

This article is about three distinct storage types:

NVS: traditional Non-Volatile Storage in mechanical disks - Hard disk, Optical disk, floppy disk, etc. Non-Volatile Storage may also refer to NVM.
NVM: storage in Non-Volatile Memory chips (Flash memory Storage) - EEPROM, SSD, NAND, etc. Non-Volatile Memory may also refer to NVMM.
NVMM storage inside Non-Volatile Main Memory chips (Re-RAM) - NVDIMM-P, specifications to be released 2018.

Answer 2

ROM that is read only memory is non volatile because all the data in it doesn't get erased after shutting down the computer and restarting it. Whereas RAM that is random access memory is volatile because all the data in it gets erased after shutting down the computer and restarting it.

Hope this helps you