The syntax of the include directive is very simple. It is the directive itself followed by a quoted name of a source file we want to include. Logically, the operation is the same as of #include keyword in C or C++. Programming in Assembly is not always simple and it is a very good idea to split your code into several source files (for example, put all your definitions of macro instructions in a separate file), then combine them all by including them in the main source.