To include another source file in an assembler source file, use the ‘include’ directive:
The argument string_literal specifies a (quoted) absolute or relative path to an included file. The base directory for the relative path is:
The directive must be on a line of its own after at least one whitespace character at the beginning of the line. The directive must not occur within a macro definition. The maximum nesting level of ‘include’ directives is 100.