ROM is a small part of a computer which means read-only memory and it provides space for the programs for booting and the startup of PC. Read only memory, shortly ROM enables an electronic device to regulate their work motion which is inserted in the integrated circuit. ROM is primarily used in various electro-mechanical devices and is less used in computer IC. ROM is a device which is mainly used for storage purposes. The data stored in ROM is not readily modifiable and the data is used to run a specific hardware with certain software, which in terms is said firmware.

The journey of first ever programmable ROM was started in 1956. In 1971, EPROM was invented which enables various erase options. With the advancement of time, electronically programmable ROM was modified and 80s was the time when ROM became more popular and user friendly. Current users are completely astonished with ROM’s flash memory and its features.

The data stored in ROM is non volatile, which means the data is stored without any power supply. Any device needs special application to change the data in ROM.

ROM is classified into five main classes:

Classical read-only memory (ROM): Classic mask programmed ROM are the oldest model of ROM. The data and program is stored permanently, which can’t be changed after manufacturing.

Programmable read-only memory (PROM): PROM is also a one tome programmable ROM which is programmed with the aid of special devices. Consequently this ROM creates internal links within the IC which is inerasable.

Erasable programmable read-only memory (EPROM): This is a type of ROM which enables a device to erase the data in ROM. When the ROM is exposed to ultra-violet (UV) ray for more than 10 minutes, the stored data is deleted and it enables to input new programs. This erasing cycle can be done 1000 times with an EPROM.

Electrically erasable programmable read-only memory (EEPROM): EEPROM is very much similar to EPROM. The main difference is that the data is erased electrically, where with EPROM UV ray is used.

Flash memory: Flash memory is the modified version of EEPROM. It is faster than EEPROM and rewriting and deleting is easy with it. Recently NAND flash has made this easier and flash memory is mostly used in electronic devices now a day.

Diode is a device which flow the current in a single direction. The threshold value is the criteria of minimum voltage which is required to find a diode in an integrated circuit. This is termed as forward break over. When ROM sends a signal of over 0.6 Volts, if the certain diode prevail in the circuit, then it response with a binary signal ‘1’. If it doesn’t exist it gives a signal ‘0’. The ROM is effective just after the whole program is properly done and executable.

ROM has its main uses in the electronic devices. It makes the primary code use easy with its versatile distinction.