1 GCC The GCC command invokes the GNU C compiler.      GCC file-spec2 Parameters file-spec     A C source file.  If no input file extension is specified, GNU C      assumes .C as the default extension.2 Qualifiers GNU C command qualifiers modify the way the compiler handles the compiliation. The following is the list of available qualifiers for GNU C:      /CC1_OPTIONS=(option [,option...]])      /DEBUG      /DEFINE=(identifier[=definition][,...])      /INCLUDE_DIRECTORY=(path [,path...]])      /MACHINE_CODE      /OPTIMIZE      /UNDEFINE=(identifier[,identifier,...])      /VERBOSE2 Linking When linking programs compiled with GNU C, you should include the GNU C library before the VAX C library.  For example,  LINK object-file,GNU_CC:[000000]GCCLIB/LIB,SYS$LIBRARY:VAXCRTL/LIB You can also link your program with the shared VAX C library.  This can reduce the size of the .EXE file, as well as make it smaller when it's running.  For example,  $ LINK object-file, GNU_CC:[000000]GCCLIB/LIB,SYS$INPUT:/OPTIONS  SYS$SHARE:VAXCRTL/SHARE (If you use the second example and type it in by hand, be sure to type  ^Z after the last carriage return)2 /DEBUG /DEBUG includes additional information in the object file output so that the program can be debugged with the VAX Symbolic Debugger. This qualifier includes very little information, so using the debugger is somewhat difficult.2 /DEFINE=(identifier[=definition][,...]) /DEFINE defines a string or macro ('definition') to be substituted  for every occurrence of a given string ('identifier') in a program. It is equivalent to the #define preprocessor directive. All definitions and identifiers are converted to uppercase unless they are in quotation marks. The simple form of the /DEFINE qualifier, /DEFINE=vms results in a definition equivalent to the preprocessor directive #define VMS 1 You must enclose macro definitions in quotation marks, as in this example: /DEFINE="C(x)=((x) & 0xff)" This definition is the same as the preprocessor definition #define C(x) ((x) & 0xff) If more than one /DEFINE is present on the GCC command line, only the last /DEFINE is used. If both /DEFINE and /UNDEFINE are present on a command line, /DEFINE is evaluated before /UNDEFINE2 /INCLUDE_DIRECTORY=(path [,path...]) The /INCLUDE_DIRECTORY qualifier provides additional directories to search for user-defined include files.  'path' can be either a  logical name or a directory specification. There are two forms for specifying include files - #include "file-spec" and #include <file-spec>.  For the #include "file-spec" form, the search order is: 1.  The directory containing the source file. 2.  The directories in the /INCLUDE qualifier (if any). 3.  The directory (or directories) specified in the logical name     GNU_CC_INCLUDE. 4.  The directory (or directories) specified in the logical name     SYS$LIBRARY. For the #include <file-spec> form, the search order is: 1.  The directories specified in the /INCLUDE qualifier (if any). 2.  The directory (or directories) specified in the logical name     GNU_CC_INCLUDE. 3.  The directory (or directories) specified in the logical name     SYS$LIBRARY.2 /MACHINE_CODE Tells GNU C to output the machine code generated by the compiler.  Note that no object file is produced when /MACHINE_CODE is specified.  The machine code is output to a file with the same name as the input file, with the extension .S.2 /OPTIMIZE    /NOOPTIMIZE Controls whether optimization is performed by the compiler.  By default, optimization is on.  /NOOPTIMIZE turns optimization off.2 /UNDEFINE /UNDEFINE cancels a macro definition.  Thus, it is the same as the #undef preprocessor directive. If more than one /UNDEFINE is present on the GCC command line, only the last /UNDEFINE is used. If both /DEFINE and /UNDEFINE are present on a command line, /DEFINE is evaluated before /UNDEFINE2 /VERBOSE Controls whether the user sees the invocation command strings for the preprocessor, compiler, and assembler.  The compiler also outputs some statistics on time spent in its various phases.