* This metacommand does not require a comment ''[[Apostrophe|']]'' or [[REM]] before it.
* {{Parameter|message}} is any text. Quotation marks are not required.
* When QB64 tries to compile an '''$ERROR''' metacommand a compilation error is triggered and {{Parameter|message}} is shown to the user. This is useful in [[$IF]] blocks.
* If there is a particular situation where you know your program will not work properly, you can prevent the user compiling and give them a helpful error message instead by checking for the condition with [[$IF]].
* An '''$ERROR''' directive not inside an conditional [[$IF]] (or [[$ELSEIF]]) block is useless because the program will '''never''' compile in that case.
;Output (IDE Status Area):Compilation check failed: REQUIRES WINDOWS QB64 VERSION 2.1 OR ABOVE on line 2 (assuming your version of QB64 doesn't meet those requirements).