What distinguished the first microprocessors like the Intel 4004 from a microcontroller?

Answer

They were essentially just the CPU core, requiring external chips for memory and I/O.

The distinction lies in the architecture; microprocessors like the 4004 provided only the CPU core, necessitating separate chips for memory and peripherals to form a functional system, whereas a microcontroller integrates all these functions onto one chip.

What distinguished the first microprocessors like the Intel 4004 from a microcontroller?
inventorcomputerelectroniccircuitmicrocontroller