看看为什么YDE没有赋值

#include<stdio.h>
#include<math.h>
float Y,D,E;
void Y_to_D(float x)
{
    D = 0.141 * x; 
    printf("%f",D);
 } 
void Y_to_E(float x)
{
    E = 0.127 * x; 
    printf("%f",E);
 } 
void E_to_Y(float x)
{
    Y = 7.869 * x; 
    printf("%f",Y);
 } 
void E_to_D(float x)
{
    D = 1.113 * x; 
    printf("%f",D);
 } 
void D_to_E(float x)
{
    E = 1.113 * x; 
    printf("%f",E);
 } 
void D_to_Y(float x)
{
    Y = 7.070 * x; 
    printf("%f",Y);
 } 
int main()
{
    float a;
    char choice;
    printf("1-RMB is converted into dollars\n");
    printf("2-RMB is converted into euros\n");
    printf("3-The dollar is converted into euros\n");
    printf("4-The dollar is converted into RMB\n");
    printf("5-Euros are converted into dollars\n");
    printf("6-Euros are converted into RMB\n");
    printf("please input your choice :");
    scanf("%c",&choice);
    printf("Please enter your amount :");
    scanf("%f",&a);
    switch(choice)
    {
        case 1 :
            Y_to_D(a);
            break;
        case 2 :
            Y_to_E(a);
            break;
        case 3 :
            D_to_E(a);
            break;
        case 4 :
            D_to_Y(a);
            break;
        case 5 :
            E_to_D(a);
            break;
        case 6 :
            E_to_Y(a);
            break;
    }
    return 0;
}

    int choice;
    scanf("%d", &choice);

或者

  case '1':
  case '2':
  ......