Where is firmware typically stored in an embedded system?

Firmware is essential software programmed into embedded systems, providing the low-level control for the device's specific hardware. This type of software needs to be permanent and persistent, which is why it is typically stored in read-only memory (ROM) or flash memory.

ROM is non-volatile, meaning it retains its contents even when the power is turned off, making it suitable for storing firmware. Flash memory, while also non-volatile, allows for the firmware to be updated when necessary, which is often required for security updates or feature enhancements in embedded systems. This ability to update is why flash memory has become a more common medium for firmware storage in modern devices.

In contrast, volatile RAM loses its data when power is lost, making it unsuitable for storing firmware. External memory cards and hard drives are also not ideal for firmware storage, as they are not typically embedded in the system and may not provide the instant access required for firmware operation in real-time applications.

Thus, the choice of ROM or flash memory reflects the needs of embedded systems to run reliable, unchanging firmware while allowing for potential updates when necessary.