/*
*        Delay functions for HI-TECH C on the PIC
*
*        Functions available:
*                DelayUs(x)        Delay specified number of microseconds
*                DelayMs(x)        Delay specified number of milliseconds
*
*        Note that there are range limits: x must not exceed 255 - for xtal
*        frequencies > 12MHz the range for DelayUs is even smaller.
*        To use DelayUs it is only necessary to include this file; to use
*        DelayMs you must include delay.c in your project.
*
*/

/*        Set the crystal frequency in the CPP predefined symbols list in
        HPDPIC, or on the PICC commmand line, e.g.
        picc -DXTAL_FREQ=4MHZ
       
        or
        picc -DXTAL_FREQ=100KHZ
       
        Note that this is the crystal fr equency, the CPU clock is
        divided by 4.

*        MAKE SURE this code is compiled with full optimization!!!
       
*/
#ifndef        XTAL_FREQ
#define        XTAL_FREQ        12MHZ                // Crystal frequency in MHz
#endif

#define        MHZ        *1000L                        /* number of kHz in a MHz */
#define        KHZ        *1                        /* number of kHz in a kHz */

#if        XTAL_FREQ >= 12MHZ

#define        DelayUs(x)        { unsigned char _dcnt;
                          _dcnt = (x)*((XTAL_FREQ)/(12MHZ));
                          while(--_dcnt != 0)
                                  continue; }
#else

#define        DelayUs(x)        { unsigned char _dcnt;
                          _dcnt = (x)/((12MHZ)/(XTAL_FREQ))|1;
                          while(--_dcnt != 0)
                                  continue; }
#endif

extern void DelayMs(unsigned char);






看上面那段E文的意思，好像调用之前要在哪里设置晶振频率，但是我在MPLAB又找不到什么地方设置！
难道在要程序当中以命令行的模式来设置？