Short for International Electrotechnical Commission, an international standards body. Responsible for standards such as the socket on the back of your PC or on your power adapter where you plug in the mains lead. According to 
Wikipedia, their standards have numbers in the range 60000–79999.
IEC320
The specification for the mains-power sockets on the back of PCs and other electrical and electronic equipment, and the corresponding plug. The same standard is used worldwide, unlike for wall sockets. Commonly known as a “kettle lead”.
Short for IEC 60320, according to
IEC958
another name for S/PDIF. This is the optical connector on your sound card or your PC’s onboard sound hardware.
Short for IEC 60958, according to
One page links to IEC:
