It depends - if it's just headphones, it's an output device. If the headset includes a microphone - it's both an input and output device.
A headset
A headset can function as both an input and an output device. It serves as an output device by producing sound for the user to hear, such as audio from a computer or phone. It can also function as an input device by incorporating a microphone to capture the user's voice for communication or recording purposes.
I assume by headset you mean something with both headphones and a microphone. I that case, it is both an input AND output device.
all in one printer, which has scanner, printer, copier, and fax
A headphone adapter will work when plugged into the heaphone output. It isn't designed to work on the input side, as most adapters are stereo, and the input on mixers is mono.
is an omr and input or output device?
both input r output
Input device.
Output, the sound is coming from the computer. Headphones are output; they produce something after receiving signal from another device, such as a computer or electronic player. When you use headphones they go in the output port of your computer.
it is an output device
output/input
output and input