4D can be lenient with coding styles and syntax. Sometimes you may write a line of code that is missing a parenthesis, or perhaps you have used the same variable name in multiple methods with conflicting types. The compiler is a good way of checking for these types of code mistakes.

In order to make the compiler catch even more mistakes, it is suggested that you enable the "All variables are typed" compilation path in the Preferences under "Design Mode / Compiler":



To access the compiler from design mode click on the Compiler icon in the toolbar:



Or to access the compiler from design mode click on the Design drop down menu then choose Compiler from the list:




Once in the compiler, press the Compile button to check for errors. Some possible results could look like:



The developer should be able to look at the results of the compiler and fix each error listed. Double clicking on an error in the compiler will take you directly to the method and line it is referring to. After fixing the code, return to the compiler and press the Compile button again

Here is a screen shot of the same code fixed:



If after fixing your code you do not want to run your application compiled, simply click on the "Clear Compiled Code" button to remove the compiled code.