3-13.c

一些简单的c51程序

#include <REG52.H>              
#include <stdio.h>                
#include <math.h>
void main (void) {

	float a,b,c,s,x1,x2;
	double t; 

	SCON = 0x50; 
TMOD |= 0x20; 
TH1 = 0xf3; 
TR1 = 1;
TI = 1; 

printf(" please input a,b,c:");
	scanf("%f %f %f ",&a,&b,&c) ;
	if(a==0.0)
		if(b!=0.0)
			printf("the root is :%f\n",-c/b);
		else if(c==0.0)
			printf("x is inexactive\n ");
		else
			printf("no root!\n");
	else
	{
		s=b*b-4*a*c;
		if(s>=0.0)
			if(s>0.0)
			{
				t=sqrt(s);
				x1=-0.5*(b+t)/a;
				x2=-0.5*(b-t)/a;
				printf("There are two different roots:%f and %f\n",x1,x2);
			}
			else
				printf("There are two equal roots:%f\n",-0.5*b/a);
		else
		{
			t=sqrt(-s) ;
			x1=-0.5*b/a; /*实部*/
			x2=abs(0.5*t/a); /*虚部的绝对值*/
			printf("There are two virtual roots:");
			printf("%f+i%f\t\t%f-i%f\n",x1,x2,x1,x2 );
		}
	}
    while (1) {};
}