_DEFINE defines a range of variable names according to their first character as a datatype.
- Variable start letter range is in the form firstletter-endingletter (like A-C) or just a single letter.
- Datatypes: INTEGER, SINGLE, DOUBLE, LONG, STRING, _BIT, _BYTE, _INTEGER64, _FLOAT
- Can also use the _UNSIGNED definition for positive numerical values only.
Explanation: Any undefined variables that start with the letters A, B, C or F will now be defined as unsigned integers. Unsigned integers can only use positive values while ordinary integers can also use negative values.
Referance: Mathematical Operations