ROM, PROM and EPROM
ROM (Read Only Memory) is a non-volatile memory that stores permanent data and instructions. The data is written during manufacturing and cannot be modified later. It is mainly used to store firmware such as the booting program of a computer.
PROM (Programmable Read Only Memory) is also non-volatile but differs from ROM in that it is initially blank. The user can program it once using a special device. After programming, the data becomes permanent and cannot be erased or altered.
EPROM (Erasable Programmable Read Only Memory) is an advanced type of PROM that allows data to be erased and reprogrammed multiple times. The stored data can be erased by exposing the chip to ultraviolet (UV) light, after which it can be reused.
| Feature | ROM | PROM | EPROM |
|---|---|---|---|
| Full Form | Read Only Memory | Programmable ROM | Erasable Programmable ROM |
| Nature | Permanent | Programmable once | Reusable |
| Programming | Manufacturer | User (once) | User (multiple times) |
| Erasing | Not possible | Not possible | UV Light |
| Usage | Firmware | Custom programming | Testing & development |