该代码允许您在星星和三角形电阻网络转换之间进行选择。还有一个退出选项。我想验证R_a，R_b，R_c等的值。然而，我在do while循环中遇到了一些麻烦。下限是1000，上限是1000000。
我打算让程序在输入值在范围内时继续运行，在输入值不在范围内时提示用户进行另一次输入。但是，到目前为止，如果值在范围内，程序将继续运行，但如果值不在范围内，程序将在给出警告后继续运行-当我希望它循环回到第一次输入提示时。
一旦正确，我将把循环添加到所有输入中。如果有人能够修复/找到这个问题，我将不胜感激。

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(void)
{
    printf("\n\n\t\tDelta and Star Converter\n\n\n");
    int choice, num, i;
    unsigned long int fact;

    while(1)
    {
        printf("1. Star \n");
        printf("2. Delta\n");
        printf("0. Exit\n\n\n");
        printf("Enter your choice :  ");
        scanf("%d",&choice);


        switch(choice)
        {
        case 1:;

        float R_a=0,R_b=0,R_c=0,R_ab,R_bc,R_ac;


        printf("Please enter the value of the Star connected resistors:\n");

          do {
        printf("R_a = ");
         scanf("%f",&R_a);
        if (R_a > 1000000) {
            printf("Please");
        } else if (R_a < 1000) {
            printf("Number to low\n");
        }else {
        }

     }while(R_a = -0);



        printf("R_b = ");
        scanf("%f",&R_b);
        printf("R_c = ");
        scanf("%f",&R_c);

        R_ab=R_a+R_b+(R_a*R_b)/R_c;
        R_bc=R_b+R_c+(R_b*R_c)/R_a;
        R_ac=R_a+R_c+(R_a*R_c)/R_b;

        printf("the equivalent Delta values are: \n");
        printf("R_ab = %.2f Ohms\n",R_ab);
        printf("R_bc = %.2f Ohms\n",R_bc);
        printf("R_ac = %.2f Ohms\n",R_ac);
        break;

        case 2:;


        printf("Please enter the values of the Delta connected resistors:\n");

        printf("R_ab = ");
        scanf("%f",&R_ab);
        printf("R_bc = ");
        scanf("%f",&R_bc);
        printf("R_ac = ");
        scanf("%f",&R_ac);


        R_a = (R_ab*R_ac)/(R_ab + R_bc + R_ac);
        R_b = (R_ab*R_bc)/(R_ab + R_bc + R_ac);
        R_c = (R_ac*R_bc)/(R_ab + R_bc + R_ac);

        printf("the equivalent Star values are: \n");
        printf("R_a = %.2f Ohms\n",R_a);
        printf("R_b = %.2f Ohms\n",R_b);
        printf("R_c = %.2f Ohms\n",R_c);
        break;

            case 0:
                printf("\n\nAdios!!\n\n\n");
                exit(0);    // terminates the complete program execution
        }
while (0) ;  }
    printf("\n\n\t\t\tThank you!\n\n\n");
    return 0;
}