The term “alphanumeric” is used to refer to the collective set of 26 Latin letters and 10 Arabic numerals used by many nations around the world. The text in this article is alphanumeric, as it includes both letters and numbers. Often, consumers are also encouraged to use alphanumeric codes as passwords, as an alphanumeric code is much more difficult to break than a code with purely letters or numbers. Many human communications use alphanumeric code, just as you do every time you write down your name and phone number or give someone your address. Arabic numerals have been used to record numbers for centuries, although they did not reach the West until around the 12th century. It took several more centuries for Arabic numerals to become widely accepted. In addition to serving as an efficient and easier to read alternative to Roman numerals, Arabic numerals also contained the important concept of zero. There are ten Arabic digits, meaning that the numeral system they represent is a base ...
Alphanumeric - You must have at least 1 number and at least 1 letter in your user name, so that it's harder for someone else to guess. At least allowable passwords seem to be going in that direction.