Symbols can be assigned specific flags to control how they can be debugged and used.
The following symbol flag options are available:
The Trace flag activates the tracing of any user-defined function (shown as a symbol within the Symbol Service window). Tracing will only occur when the symbol is a function, and the expression being evaluated uses the symbol name as a function (not as a local variable name, for example).
This flag intercepts attempts to assign values to protected symbols. For instance, the symbol PI is a protected symbol. All symbols that are the names of built-in AutoLISP functions are assignment-protected by default.
If this flag is set, a breakpoint occurs at each function invocation, regardless of whether the function was loaded with debugging information. The De flag is tested at each function invocation, not during load or defun execution.
If the Ea flag is set, the function associated with this symbol is defined as an external subroutine. This makes the function available to ObjectARX and Managed .NET applications.