ex12.c

来自「《8051系列单片机C程序设计完全手册》的光盘中的所有源代码」· C语言 代码 · 共 53 行

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

#include <stdio.h>                /* prototype declarations for I/O functions */


#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                        */


/*------------------------------------------------
The main C function.  Program execution starts
here after stack initialization.
------------------------------------------------*/
void main (void) {

	float price,tax=0;
/*------------------------------------------------
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
	printf("input price:");
	scanf("%f",&price);
	if(price>=10000.0)
	{
		tax=0.05*(price-10000)+tax; price=10000;
	}
	if (price>=5000.0)
	{
		tax=0.03*(price-5000)+tax;price=5000; 
	}
	if(price>=1000.00)
	{
		tax=0.02*(price-1000)+tax;
	}
	printf("the tax=%10.3f\n",tax);
/*------------------------------------------------
Note that an embedded program never exits (because
there is no operating system to return to).  It
must loop and execute forever.
------------------------------------------------*/
  while (1) {};
}