Computer - Read Only Memory (ROM)

What is ROM?

ROM is a non-volatile memory that stores data permanently. Advanced ROM data can be erased and rewritten. The information in ROM can only be accessed, making it perfect for use in computers as it enables quick access to data without the need for constant data rewriting. Important data, like BIOS settings and operating system instructions, are stored in these memories, which are crucial for the proper functioning of your computer. Without them, your computer would essentially be “brain dead,” so they must continue to work properly at all times!

ROM is an efficient storage method requiring minimal effort and maintenance, capable of holding instructions and various types of data.

Characteristics of Read Only Memory (ROM)

The primary characteristics of ROM are as follows −

• ROM is Non-volatile in nature.
• Advanced ROM can be rewritten.
• Data or information stored on ROM can be read-only.
• ROM holds its data even when power is turned off.
• The read-only characteristic ensures data stability and integrity.
• ROM utilization occurs during the computer’s boot-up procedure.

How does Read Only Memory (ROM) Work?

ROM functions by using memory cells, which are composed of transistors arranged in series to enable the flow of electrical current when powered. This current passing through the transistors generates a magnetic field that retains the data in the memory cell until it is erased by another signal passing through the transistor. The information stored in these cells cannot be altered or deleted unless directed by an external entity such as a computer processor or hard drive controller.

Overall, inside the computer, a small but durable battery powers the ROM. Its two essential components are the decoder and OR logic gates. Binary input from the ROM is processed by the decoder, which then produces the decimal equivalent as output. The decimal output of the decoder is used as the input for the OR gates in the ROM.

ROM is akin to an array of disks. The system can be activated and deactivated using a grid of rows and columns. Each element of the array is assigned to a specific memory element on the ROM. A diode is used to connect the relevant components. When a request is sent, the address provided is used to locate the specific memory location. The value extracted from the ROM chip must match the value in the array’s selected element.

Types of Read-Only Memory (ROM)

Based on its characteristics and uses, ROM is broadly classified into four different types −

1. MROM (Masked Read-Only Memory)

MROM stands for Masked Read-Only Memory. This memory device is no longer used nowadays due to obsolescence. Manufacturers are using this memory to store software and information during the manufacturing process. Therefore, it is impossible to alter, reprogram, or erase this type of pre-programmed chip later.

Applications of MROM

It is most widely used in Network Operating Systems and Server Operating Systems.

2. PROM (Programmable Read-Only Memory)

PROM stands for Programmable Read-Only Memory. Generally, it’s a blank memory chip. It can be programmed during manufacturing and cannot be changed or erased. A PROM programmer or PROM burner is used to write information to a PROM. The process of programming a PROM chip is commonly known as “PROM Burning.” Once programmed, the chip’s content cannot be changed. As a result, it is also known as a one-time programmable device.

Applications of PROM

It is most widely used in Computer Bios, TV Remote, Video game consoles and nowadays a day used in Mobile Phones.

3. EPROM (Erasable Programmable Read-Only Memory)

EPROM stands for Erasable Programmable Read-Only Memory. It can be programmed and later erased by exposing it to strong ultraviolet light. After being erased, the EPROM can be reprogrammed. EPROM is a type of read-only memory chip that may erase previously programmed data. High voltage can be used to program the programmable read-only memory to write data, which is then retained until exposed to ultraviolet light for 10 minutes or more.

Applications of EPROM

It is most widely used in Video cards, Memory sticks, BIOS chips, and Modem.

4. EEPROM (Electrically Erasable Programmable Read-Only Memory)

EEPROM stands for Electrically Erasable Programmable Read-Only Memory. It is an advanced type of ROM that can be erased and reprogrammed electrically. This operation can be repeated indefinitely, and the computer system can do it while running. The EEPROM allows users to program and erase any desired spot. It is erased byte by byte rather than the full chip. As a result, reprogramming is flexible and takes less time to complete the process.

Applications of EEPROM

It is most widely used in Bios Chip and Microcontrollers for Smart Cards.

5. Flash Memory

It is a type of EEPROM that can be erased and reprogrammed in blocks rather than one byte at a time which allows for faster and more efficient operations. It is widely employed as storage in modern devices such as USB drives, memory cards, and SSDs. A modern variant of EEPROM is flash memory. With its newer designs and high endurance, it may be erased and rewritten faster than typical EEPROMs.

Applications of Flash Memory

It is most widely used in storage devices like USB drives, memory cards, and SSDs.

Advantages of Using (Read Only Memory) ROM

The primary advantages of ROM are as follows −

• It is non-volatile and less expensive than RAM.
• Its circuit design is simple as compared to RAM.
• No need to refresh it.
• ROM provides fast data access.
• It is reliable.
• Data remains intact and uncorrupted.
• It maintains data integrity and security.

Applications of Read Only Memory (ROM)

There are various applications of ROM. Some of those applications are as follows −

• Supports the Booting Process − It supports the booting process of the computer and loads the operating system.
• Input/output (I/O) Tasks − ROM performs large I/O tasks.
• Stores Data − ROM stores data and updates firmware software.
• Embedded Systems − ROMs are most widely used in microwaves, washing machines, and related appliances where firmware controls operations.
• Consumer Electronics − It is used in modern smartphones for storing bootloaders and firmware.
• Computer BIOS − It provides support for basic Input / Output System (BIOS) in PCs.

ROM is an essential memory device in different electronic systems due to its impact use like reliability, security, and cost-effectiveness.

RAM Vs. ROM

The primary difference between RAM and ROM are as −