Unlike a general-purpose system such as a home computer, usually a development board contains little or no hardware dedicated to a user interface.
The reason for the existence of a development board was solely to provide a system for learning to use a new microprocessor, not for entertainment, so everything superfluous was left out to keep costs down.
The most important feature of the microprocessor development board was the ROM-based built-in machine language monitor, or "debugger" as it was also sometimes called.
[5] Often the board has some kind to expansion connector that brought out all the necessary CPU signals, so that an engineer could build and test an experimental interface or other electronic device.
External interfaces on the bare board were often limited to a single RS-232 or current loop serial port, so a terminal, printer, or Teletype could be connected.