IB Statements/unset
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UNSET directive
Syntax: UNSET symbolic-constant
Discussion: The UNSET statement is a compiler directive. As such, it causes an action to occur when the program is compiled, not when the program is executed. The UNSET directive can appear anywhere in an Internet Basic source program. To facilitate the manipulation of symbolic constants for conditional compilation purposes, the Internet Basic language includes the UNSET directive. The UNSET directive clears the definition of the symbolic constant (i.e., "un-defines" it). This directive is particularly useful when working with the .IFDEF and .IFNDEF directives.
Example: UNSET ABC ! un-define the symbolic constant named ABC