Asus X451MA - Manual (Page 22)

 Notebook PC E-Manual
VGA port
This port allows you to connect your Notebook PC to an
external display.
HDMI port
This port is for the HDMI (High-Definition Multimedia Interface)
connector and is HDCP compliant for HD DVD, Blu-ray, and
other protected content playback.
USB 2.0 port
This USB (Universal Serial Bus) port is compatible with USB .0
or USB 1.1 devices such as keyboards, pointing devices, flash
disk drives, external HDDs, speakers, cameras and printers.
USB 3.0 port
The USB (Universal Serial Bus) 3.0 port provides a transfer rate
of up to  Gbit/s and are backward compatible to USB .0.
Headphone output/microphone input combo jack port
This port allows you to connect your Notebook PC to amplified
speakers or headphones. You can also use this port to connect
your Notebook PC to an external microphone.