Monitor is not plugged in or monitor is not plugged in to computer
nothing can affect a computer
Assuming there is power to the monitor (the 'on' indicator is illuminated)... Check the cable from the monitor to the CPU is connected... (try another cable to be sure). If that's okay - the next thing to check would be the graphics card inside the computer (best done by a competent technician).
If nothing happens when you press the power button, make sure all the wires are connected. make sure that both the computer and the monitor are plugged into a power source. Also, make sure that the monitor is connected to the computer. If it still does not turn on, you might be having a problem with one of the components in your computer. At this point I would take it to a specialist and have them figure out what the problem might be.
When the computer is not processing anything at all. The computer light is on the monitor light is not but nothing is processing through the computer therefore no data is coming up on the monitor, not even the startup menu.
Probably nothing bad. However, be certain that your computer is rated for this high of voltage.
It will be blank..nothing is saved to your moniter.
Go to a computer specialist!
Just selling the monitor can do no harm. Nothing is saved to the monitor itself, it is only a display device and will display data of the computer to which it is attached.
The Answer is: NOTHING. Nothing in a computer "tells it what to do." You ask it a question... The processor processes the question, and calculates the answer... The answer is then processed into a code that the monitor can turn into an image... The motherboard directs this code to the monitor... Your question is answered. (brief explanation of how a computer really works)
This depends on what computer and what monitor we are talking about. Back in the old days the monitor had no two way contact withthe comuter and controlled nothing. More current Monitors are plug and play so the monitor tells the computer what it is and how to talk to it. So to a very limited extent, yes. Then the touch screen monitors that are common now do control what happens inside the computer.
Have you tried selecting the input on your monitor options menu?
It likely that you plugged your headphones into the wrong jack. There should be a jack for your headphones on your computer that has the head-phones label on it, not the one with speakers or for a microphone.