The MAC is useful as a unique computer indentifier for software protection schemes. Intel’s Pentium class machines have a unique serial number burned into their silicon that can also serve that purpose. AMD’s do not.

In Java 1.6+ there is java.net.NetworkInterface. getHardwareAddress which will get you the hardware address of an adapter, usually the MAC. You need sufficient privilege to use it.

Here’s how to display a long MAC address in hex with the traditional dashes.

MAC also stands for Message Authentication Codes. They are digital signatures used to verify that a piece of data originated with a given party and that it has not been tampered with. A MAC mechanism that is based on cryptographic hash functions is referred to as HMAC. HMAC can be used with any cryptographic hash function, e.g., MD5 or SHA-1, in combination with a secret shared key. How HMACs work is specified in RFC 2104. JCE has support for HMAC-MD5 and HMAC-SHA1.

The term Mac (not all caps) refers to Apple’s line of computers, the MacIntosh, deliberately spelled differently from the McIntosh apple tree species after which it was named and McIntosh the maker of high end stereo equipment, and presumably to avoid dealing with lawyers from that Scottish McFood company.