6.1. Predefined Macros

            One technique through which machine unavoidable machine
       dependencies  may  be  managed is the predefined macros pro-
       vided by each compiler to identify the target processor  and
       operating system (if any). These are defined by the compiler
       driver  and  may  be  tested  with  conditional  compilation
       preprocessor directives.

            The macros defined by various compilers are  listed  in
       table 2. These can be used as shown in the example in fig .

           ___________________________________________
          |_Macro_______________Defined_for__________|
          | i8051    8051 processor family           |
          | i8086    8086 processor family           |
          | i8096    8096 processor family           |
          | z80      Z80 processor and derivatives   |
          | m68000   68000 processor family          |
          | m6800    6801, 68HC11 and 6301 processors|
          | m6809    6809 processor                  |
          | DOS      MS-DOS and PC-DOS               |
          | CPM      CP/M-80 and CP/M-86             |
          | TOS      Atari ST                        |
          |__________________________________________|


                    Table 2. Predefined Macros


        #if     DOS
        char *  filename = "c:file";
        #endif  /* DOS */
        #if     CPM
        char *  filename = "0:B:afile";
        #endif  /* CPM */