A large collection of predefined functions exist that provide access to the
machine being debugged, as well as those which perform various operations
on values of the data types supported by System Debug.
Syntactically, a function reference appears as an operand in an expression and is denoted by its name, followed optionally by a list of parameters
surrounded by parentheses. Multiple parameters are separated from one
another by either spaces or commas. Functions evaluate to a single value
of some type.
Detailed descriptions of all the System Debug predefined functions may be found in
chapter 8.
