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  • 指针在函数间传递实质

    /*------------------------------------------------------------------------------
    HELLO.C

    Copyright 1995-1999 Keil Software, Inc.
    ------------------------------------------------------------------------------*/

    #include <REG52.H>                /* special function register declarations   */
                                      /* for the intended 8051 derivative         */

    #include <stdio.h>                /* prototype declarations for I/O functions */
    #include <stdlib.h>
    #include <string.h>
    #include <ABSACC.H>


    #ifdef MONITOR51                         /* Debugging with Monitor-51 needs   */
    char code reserve [3] _at_ 0x23;         /* space for serial interrupt if     */
    #endif                                   /* Stop Exection with Serial Intr.   */
                                             /* is enabled                        */
    char *gpch=100;
    void chadr(char *chr)
    {
     chr=gpch;
    }
     void chva(char *chr)
     {
      *chr=20;
     }
    /*---------------------------------------------
    The main C function.  Program execution starts
    here after stack initialization.
    ------------------------------------------------*/
    void main (void) {
     char testchr=10;
    /*------------------------------------------------
    Setup the serial port for 1200 baud at 16MHz.
    ------------------------------------------------*/
    #ifndef MONITOR51
        SCON  = 0x50;          /* SCON: mode 1, 8-bit UART, enable rcvr      */
        TMOD |= 0x20;               /* TMOD: timer 1, mode 2, 8-bit reload        */
        TH1   = 221;                /* TH1:  reload value for 1200 baud @ 16MHz   */
        TR1   = 1;                  /* TR1:  timer 1 run                          */
        TI    = 1;                  /* TI:   set TI to send first char of UART    */
    #endif

    /*------------------------------------------------
    Note that an embedded program never exits (because
    there is no operating system to return to).  It
    must loop and execute forever.
    ------------------------------------------------*/

     printf("init=%bd/n",testchr);
     chva(&testchr);//变量地址传入函数,函数直接对变量操作;而不是地址
     printf("after=%bd/n",testchr);
     chadr(&testchr);//地址传入函数后,存储在栈中,在函数中修改无效,返回消失,还是原来的地址
     printf("changeaddr=%bd/n",testchr);
      while (1) {
        P1 ^= 0x01;           /* Toggle P1.0 each time we print */

      }
    }

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  • 原文地址:https://www.cnblogs.com/fedorayang/p/5094233.html
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