Before a macro runs first time, or after editing, QM at first compiles it. Also compiles when you click menu Run -> Compile, or when you create exe. The compiled code is not native machine code, but it is executed much faster than a non-compiled script.
If there are syntax errors, the compiler stops, shows error message in QM output, and highlights that statement or part of statement.
Debugging - finding and fixing errors.
To quickly disable/enable a single line or several selected lines, right click the selection bar.
To handle run-time errors, use err.
Debugging and error handling functions and variables are in _debug category.
See also: common errors