Variables

• What are variables in progamming?
• They're like mathematical variables but they have a direct implementation in computer hardware.
• There is computer memory associated with a variable (e.g. 2 bytes, 32 bytes, or 2000 bytes).
• It usually has a type associated with (e.g. boolean, integer or string)
• The variable persists for a time specified by the program, then is used for some other program or perhaps reused for your program.
• You can inspect the variable (e.g. ==, <)
• You can change the variable (=)
• Clips uses lists for its variables. They call them facts.
• So, you define a fact by for instance a 3-ary predicate like:
  (age-of Chris 39).
• The developer and the reader nows that the age of Chris is 39, when he sees this fact.