# Microcontroller

![Don't belittle it.](block:OpenComputers:microcontroller)

Microcontrollers are built using a [microcontroller case](../item/microcontrollerCase1.md) in the [assembler](assembler.md). They have less functionality compared to [computers](../general/computer.md), but are cheaper to build. In particular, they *can not* interact with external components.

Microcontrollers can take various components, such as [CPUs](../item/cpu1.md), [memory (RAM)](../item/ram1.md), and Expansion cards. Microcontrollers are unable to contain a [hard disk drive](../item/hdd1.md), but do contain a slot for an [EEPROM](../item/eeprom.md), which can be programmed for very specific tasks. They have an advantage over [computer cases](case1.md), in that they can also make use of some upgrades, such as the [piston upgrade](../item/pistonUpgrade.md).
