ROM is a non-volatile storage memory used for storing useful data required for the booting of a device. It is called non-volatile because even if the system goes off, the information stored in the ROM will still be retained.
Just as the name signifies, data stored in ROM are read only and if there is any need that such data would have to be modified, it requires a lot of hard work. A frequent used of ROM is for firmware update.
In addition, read-only memory (ROM) is also known as firmware. It is an integrated circuit that is programmed with specific data when manufactured. Its chips are used not only in computers but in most electronic devices as well.
Types of ROM
The following are the types of ROM based on their behavior:
1. MROM
MROM is an acronym for Masked Read Only Memory. It is a pre-programmed ROM. It allowed data to be written but altering the data cannot be done anyhow.
2. PROM
PROM is an acronym for Programmable Read Only Memory. It is a memory chip that allows the user to write data to it only once. Once data is written, it cannot be modified again.
3. EPROM
EPROM simple means Erasable and Programmable Read Only Memory. It is a memory chip that can be used for storage of data as well as erase if there is any need to make changes.
In order for the written data to be erased, the EPROM must be exposed to ultra-violet radiation for the EPROM to be discharged so that new content can be written
4. EEPROM
Electricity Erasable Programmable Read Only Memory or simply EEPROM is a memory that can be used for storage. As the name implies, data written to this memory chip can be erased but it will be one byte at a time rather than erasing everything once hence making the erasing process somehow delay compared to the ROMs that allow complete deletions.
5. FLASH ROM
This is a type of ROM that stores information memory cells made from transistors known as floating-gate transistors with an access time around 45 to 90 seconds. One of its advantages is the ability for it to be reprogrammed without removing it from the computer system. Unlike EEPROM where only 1 byte of data can be written or deleted at a particular time, FLASH ROM can take up to 512 bytes of data thereby making it more faster than EEPROM.
It is an advanced version of EEPROM. It stores information in an arrangement or array of memory cells made from floating-gate transistors. The advantage of using this memory is that you can delete or write blocks of data around 512 bytes at a particular time. Whereas, in EEPROM, you can delete or write only 1 byte of data at a time. So, this memory is faster than EEPROM.
Uses of FLASH ROM
- FLASH ROM is used for data storage and transfer between PC and digital devices.
- It is used in digital cameras, Solid State Drives (SSDs), USB flash drives e.t.c
- Most modern computer BIOS is stored in FLASH ROM known as FLASH BIOS
Advantages of ROM
- It is cheaper to acquire compare to RAM
- It is non-volatile memory.
- It is more reliable as compared to RAM.
- Its circuit is simple as compared to RAM.
- It doesn’t need refreshing time because it is static.
- It is easy to test.
Disadvantages of ROM
- It is difficult to modified due to its read only nature
- It is very slow compared to RAM