The scope of PHI can be broad; however, medical information that an employer receives in its role as an employer (and not as the sponsor or administrator of a group health plan), is generally not PHI subject to HIPAA.
Alphabetic characters are the 26 letters of the alphabet. Numeric's are the ten digits. Alphanumerics are both. Some of the special characters on a standard keyboard do not work for usernames or passwords.
The ASCII Character Set. ASCII stands for the American Standard Code for Information Interchange. It was designed in the early 60's, as a standard character set for computers and electronic devices. ASCII is a 7-bit character set containing 128 characters. It contains the numbers from 0-9, the upper and lower case English letters from A to Z, and some special characters. The character sets used in modern computers, in HTML, and on the Internet, are all based on ASCII.