5.2.3 INCLUDE

Another method of modularizing your source code is to INCLUDE 
entire files within the main file. This is possible using either 
the preprocessor %INCLUDE (discussed in Chapter 8, Macros and 
Conditional Assembly), or an assembly-time INCLUDE pseudo-op:
 
   INCLUDE "header.h"

Note that the INCLUDE must not begin in the first column. The 
double quote marks (" ") around the file to be included mean that
the file hearder.h resides in the current directory.  Surrounding
the filename with angle brackets (< >), as in:

  
   INCLUDE <header.h>

means that the file resides in the MS-DOS INCLUDE directory. This
directory is 'set' similarly to the MS-DOS PATH variable (see 
section 1.5.3).

Note: if an included file has an END statement in it, assembly 
will cease at that point, just as if you had typed the END 
statement into the source file itself.