/*------------------------------------------------------------------------------
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 */
}
}