Input. (Although some game controllers have tactile feedback and so are output devices as well as input devices.)
A computer system that is part of a larger device and which controls how that device operates is an embedded system. Usually the processor constantly runs a single control program which is permanently kept in ROM (Read Only Memory).
ROM is used to make a section of main memory read-only. Main memory looks the same as before to the processor, except a section of it permanently contains the program the processor is running. This section of memory retains its data even when power is off.
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, and even more in its audio system. For instance, each airbag is controlled by its own computer chip. Digital cameras, DVD players, medical equipment, and even home appliances contain dedicated processors.
The overwhelming majority of processor chips are used in embedded systems. Less than 1% of processor chips are used in the familiar desktop computer!
Your automobile engine is controlled by a computer. Do you think that this computer has: