Volatile vs Non-Volatile Memory

Describe the difference between volatile and non-volatile memory in a microcontroller. What is each type used for, and what trade-offs matter in practice?

Volatile Memory

Volatile memory requires power to retain its contents. In microcontrollers, this usually refers to RAM, which stores temporary data such as stack frames, heap allocations, and runtime variables.

counter = 0  # Stored in RAM while the program is running

Non-Volatile Memory

Non-volatile memory keeps data even when power is removed. In microcontrollers, this is commonly flash memory, EEPROM, or ROM, and it stores firmware, calibration values, and persistent configuration.

// Firmware image is stored in flash and loaded after reset

Performance and Write Behavior

Volatile memory is typically faster to read and write and supports frequent updates. Non-volatile memory is slower to write, may require erase cycles, and often has limited write endurance.

Typical Usage Split

Code and persistent settings usually live in non-volatile memory, while actively changing program state lives in volatile memory. This separation helps balance speed, persistence, and hardware limits.