Difference b/w microcontroller and computer

Computer is made-up of Processor which requires I/O Peripherals that are externally connected, making it bulky & complex design.
While, Microcontroller has all I/O peripherals embedded inside a single chip. Due to this, Microcontroller is also called mini-computer.
However, Microcontroller cannot match the clock-speed of Computer(Hence less processing speed), which is obvious because you can simply add external I/O peripherals like RAM,ROM to microprocessor but you cannot do so in microcontroller. In microcontroller the RAM & ROM size is fixed & after IC being manufactured you cannot change it.