Digital Input/Output, also known as DIO, refers to a feature of microcontrollers that allows them to detect logic states and output logic states. Digital Inputs detect if a voltage is above or below a specific threshold, and Digital Outputs allow a microcontroller to control a voltage output. LabJacks are devices that have DIO ports, and these ports may be labeled with different names such as IO, D, FIO, EIO, CIO, or MIO, depending on the specific device. Each digital I/O port can be configured as an input or output, and further configured as either high or low output.