A microcontroller (MCU) integrates the CPU core, program memory (flash), data memory (SRAM), and peripherals (GPIO, timers, ADC, UART, etc.) onto a single chip, it's a complete, self-contained computer that boots from internal flash in milliseconds and needs almost no external parts. A microprocessor (MPU, in the application-processor sense) is essentially just the CPU; it has no usable on-chip program/data memory, so it requires external DRAM, external storage (eMMC/flash), and power-management support, and it runs a full operating system like Linux. The defining difference is integration and memory, not clock speed: the MCU trades raw compute for self-containment, low power, instant-on operation, and deterministic timing, while the MPU trades those for far more memory and compute and an OS ecosystem. Many real products use both, an MPU for the rich application and an MCU as a low-power real-time co-processor.
Embedded Systems Fundamentals · Interview question
What's the difference between a microcontroller and a microprocessor?
A strong answer
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From the lesson
What Is an Embedded System?
A computer dedicated to one job inside a larger device, and the MCU-vs-MPU choice (everything-on-one-chip vs an application processor running Linux) that frames every design.