RAM |
ROM |
| It is a read-write memory | It is a read only memory |
| It is a volatile memory | It is a non-volatile memory |
| Random Access Memory | Read Only Memory |
| Data can be modified | Data cannot be modified |
| Size is larger than ROM | Size is smaller than RAM |
| RAM is costlier | ROM is cheaper |
| Types are Static and Dynamic RAM | Types are PROM, EPROM, EEPROM |
SRAM(Static RAM) |
DRAM(Dynamic RAM) |
| Uses transistor to store a single bit of data | Uses a separate capacitor to store each bit of data |
| Does not need periodic refreshment to maintain data | Needs periodic refreshment to maintain the charge in the capacitors for data |
| Structure is complex | Structure is simple |
| More expensive than DRAM | Less expensive than SRAM |
| Faster than DRAM | Slower than SRAM |
| Used in cache memory | Used in main memory |
PROM(Programmable ROM) |
EPROM(Erasable Programmable ROM) |
EEPROM(Electrical Erasable Programmable ROM) |
| Can be modified only once by a user | Can be erased by exposing it to UV light and can be reprogrammed | Programmed & erased electrically |
| Once put, program cannot be erased | Can be reprogrammed | Can be reprogrammed |
| Developed by Weng Tsing Chow in 1959 | Developed by Dov Frohman at Intel in 1971 | Developed by George Perlegos at Intel in 1978 |