To connect a computer to an HDTV, the computer must have an output matching an input port on the TV. Most HDTVs support one of the computer output standards -- HDMI, DVI or VGA -- for connecting a PC to a TV. To enable audio, the computer must usually be connected to the TV or a sound system with a separate cable.
Almost all HDTVs have either HDMI, DVI or VGA inputs; however, not all computers' outputs match the TVs' inputs. For computers without matching video outputs, a USB adapter enables video output to connect to a TV.
It is preferred to use a digital standard like HDMI or DVI over the analogue standard VGA. At resolutions of 1080p and higher, picture quality through VGA starts to diminish and may have input delay, causing the video to be out of sync with the audio.
As of 2015, HDMI is the only standard that supports audio transfer as well as video. Not all video cards have HDMI output, and some video cards only support video through HDMI. For computers without HDMI audio functionality, a separate audio cable is used to connect the computer to the TV or a separate audio system such as a stereo or computer speakers.