How does read-only memory differ from random-access memory?

Random-access memory (RAM) and read-only memory (ROM) are both forms of primary memory accessible to the central processing unit (CPU), but they differ significantly in their function, volatility, and ability to be modified.1

Key Differences

• Modifiability: RAM allows the CPU to both read and write data directly and quickly, making it a "working area" for active programs and application data. In contrast, ROM stores data that typically cannot be modified during regular computer operation. While some specialized types of ROM—such as EPROM or flash memory—are rewritable, the process is far more time-consuming than reading and is generally reserved for updates or error correction.12
• Volatility: RAM is volatile, meaning it only retains data while the computer is powered on. ROM is nonvolatile; it does not lose its contents when power is turned off, making it ideal for essential operations like the BIOS or the bootstrap program that loads the operating system.12
• Purpose: RAM is designed for high-speed data access to keep programs responsive, whereas ROM is used to store permanent, essential instructions required for a computer's operation.21