Character classes

Character classes: For the purposes of authentication and password complexity, there are four possible character classes: 

• Upper case alphabetic (e.g. A-Z)
• Lower case alphabetic (e.g. a-z)
• Numeric (e.g. 0-9)
• Special characters (e.g.!@#$%~).

A password with all four character classes might be:  "Always b3 Secure." 

1. it has upper case alphabetic: "A" and "S"
2. it has lower case alphabetic: "always b ecure"
3. it has a number: "3"
4. it has a special character: "." (period)