With an HDMI output on your laptop, you can send digital video signals to a projection screen or a high-definition television set that has an HDMI input port. However only laptops equipped with an HDMI port can make a direct connection with an HDMI cable. Without an HDMI port, you can make the connection using auxiliary equipment, but the type depends on how your laptop is equipped.
Laptop Video Outputs
Depending on the video card installed, your laptop may or may not have an auxiliary video output for external screen presentations. If it does have an output, it could be digital or analogue. If it has a digital video interface output, you can use an adaptor to add the HDMI feature. If it has an analogue output, you need a converter. If it has neither, you need an external video card that supports HDMI to add it to your laptop.
Digital Video Adapter
Digital video interface was the predecessor to HDMI and uses the same basic technology, only without adding audio. DVI uses a 24-pin "D" type connector and HDMI uses a flat plug with 19 "edge" connectors. An adaptor cable has a DVI connector on one end and an HDMI on the other, with the wires arranged to transport the appropriate signals from one to the other without the need for electronic conversion. I your laptop has a DVI output, plug on end of the adaptor cable into it and the other into an HDMI device.
Analogue Video Conversion
If your laptop has a video output in any of the analogue formats, you can add HDMI by using an converter. Common laptop analogue outputs include composite video which uses a single RCA push-in connector, S-video which uses a round four-pin connector, video graphics array which uses a 15-pin connector and component video which uses three RCA connectors. Converters may have inputs for one or more formats, depending on the make and model. Plug the video output from you laptop into the input connectors of the converter to add HDMI.
No Video Output
If your laptop has no video outputs, and you have a free USB port, you can use an external video card to add the HDMI feature. However, your laptop must have the capabilities required by the video card. Check for free hard drive space, operating system, RAM size, processor type and speed and the resolution of the video adaptor and monitor in your laptop and compare them to the requirements of the external video card.