Input. (Although some game controllers have tactile feedback and are output devices as well as input devices.)
A computer system that is part of a larger machine and which controls how that machine operates is an embedded system. Usually the processor constantly runs a single control program which is permanently kept in ROM (Read Only Memory).
The overwhelming majority of processor chips are used in embedded systems. Only 0.2% of processor chips are used in the familiar desktop computer!
A typical embedded system is a cell phone. This is obvious, but there are many less obvious embedded systems. Your car contains dozens of processors, even not counting the audio system. For example, each airbag is controlled by its own computer chip.
Your automobile engine is controlled by a computer. Do you think that this computer has: