求方程(副程式練習版)

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int get_problem()
{
    int select;
    printf("please select your mode:\n"
           "(1)tow-point form\n"
           "(2)point-slope form\n"
           "(3)quite\n");
    scanf("%d",&select);
    return select;
}
void get2_pt(double *x,double *y)
{
    printf("Enter the x-y coordinates of the point separated by a space=> ");
    scanf("%lf%lf",x,y);
}
void get2_pt_slope(double *slope)
{
    printf("Enter the slope=> ");
    scanf("%lf",slope);
}
void slope_intcpt_form2_pt(double x[2],double y[2],double *m,double *b)
{
    *m=(y[1]-y[0])/(x[1]-x[0]);
    *b=y[1]-(*m)*x[1];
}
double intcpt_form_pt_slope(double *x,double *y,double *m)
{
    return (*y-(*m)*(*x));
}
void display2_pt(double x[2],double y[2])
{
    printf("\nTwo-point form");
    printf("\n    (%.2lf-%.2lf)",y[1],y[0]);
    printf("\nm = --------------");
    printf("\n    (%.2lf-%.2lf)\n\n",x[1],x[0]);
}
void display_pt_slope(double x,double y,double m)
{
    printf("\npoint-slope form");
    printf("\ny - %.2lf = %.2lf ( X - %.2lf )\n\n",y,m,x);
}
void display_slope_intcpt(double b,double m)
{
    printf("\nSlope_intercept form");
    if(b>0)
        printf("\n y = %.2lfX + %.2lf\n\n",m,b);
    else if(b<0)
        printf("\n y = %.2lfX - %.2lf\n\n",m,-1*b);
    else if(b==0)
        printf("\n y = %.2lfX \n\n",m);
    system("pause");
    system("cls");
}
int main()
{
    int loop=0;
    double x[2],y[2],m,b;
    while(loop==0)
    {

       switch(get_problem())
       {
        case 1:
            get2_pt(&x[0],&y[0]);
            get2_pt(&x[1],&y[1]);
            slope_intcpt_form2_pt(x,y,&m,&b);
            display2_pt(x,y);
            display_slope_intcpt(b,m);
            break;
        case 2:
            get2_pt_slope(&m);
            get2_pt(&x[0],&y[0]);
            b=intcpt_form_pt_slope(&x[0],&y[0],&m);
            display_pt_slope(x[0],y[0],m);
            display_slope_intcpt(b,m);
            break;
        case 3:loop=1;
            break;
        default:printf("error\n");
                system("pause");
                system("cls");
            break;
       }
    }
    return 0;
}