Using the #include Directive when Compiling Source in a Data Management File

The following table indicates the search path the compiler takes for source physical files. See the default file names and search paths below.

Table 1. Search Path for Source Physical Files
Filename	Member	File	Library
mbr	mbr	default file	default search
file/mbr¹	mbr	file	default search
mbr.file	mbr	file	default search
lib/file/mbr	mbr	file	lib
lib/file(mbr)	mbr	file	lib
Note: ¹ If the include file format <file/mbr.h> is used, the compiler searches for mbr in the file in the library list first. If mbr is not found, then the compiler searches for mbr.h in the same file in the library list. Only "h" or "H" are allowed as member name extensions.

If library and file are not specified, the preprocessor uses a specific search path depending on which delimiter surrounds the filename. The < > delimeter specifies the name as a system include file. The " " delimiter specifies the name as a user include file.

The following describes the search paths for the #include directive used by the compiler.

Default file names when the library and file are not named (member name only):

Include type

Default File Name

<>

QCSRC for the C compiler, STD for the C++ compiler

” "

The source file of the root source member, where root source member is the library, file, and member determined by the SRCFILE option of the Create Module or Create Bound Program commands.
Default search paths when the filename is not library qualified

Include type

Search path

<>

Searches the current library list (*LIBL)

" "

Checks the library containing the root source member; if not there, the compiler searches the user portion of the library list, using either the filename specified or the file name of the root source member (if no filename is specified); if not found, the compiler searches the library list (*LIBL) using the specified filename.
Search paths when the filename is library qualified (lib/file/mbr)

Include Type

Search Path

<>

Searches for lib/file/mbr only

" "

Searches for the member in the library and file named. If not found, searches the user portion of the library list, using the file and member names specified.

User includes are treated the same as system includes when the *SYSINCPATH option has been specified with the Create Module or Create Bound Program commands.

The preprocessor resolves macros on a #include directive. After macro replacement, the resulting token sequence must consist of a file name enclosed in either double quotation marks or the characters < and >. For example:

#define MONTH <july.h>
#include MONTH

Usage

If there are a number of declarations used by several files, you can place all these definitions in one file and #include that file in each file that uses the definitions. For example, the following file defs.h contains several definitions and an inclusion of an additional file of declarations:

/* defs.h */
#define TRUE 1
#define FALSE 0
#define BUFFERSIZE 512
#define MAX_ROW 66
#define MAX_COLUMN 80
int hour;
int min;
int sec;
#include "mydefs.h"

You can imbed the definitions that appear in defs.h with the following directive:

#include "defs.h"

One of the ways you can combine the use of preprocessor directives is demonstrated in the following example. A #define is used to define a macro that represents the name of the C or C++ standard I/O header file. A #include is then used to make the header file available to the C or C++ program.

#define IO_HEADER   <stdio.h>
      .
      .
      .
#include IO_HEADER   /* equivalent to specifying #include <stdio.h>  */
      .
      .
      .

C++0x Beginning of C++0x only.

In C++0x, the changes to header and include file names in the C99 preprocessor are adopted to provide a common preprocessor interface for C and C++ compilers. The first character of a header file name in an #include directive must not be a digit in C++0x. For more information, see C99 preprocessor features adopted in C++11 (C++11).

C++0x End of C++0x only.