C语言程序 自动售货机 怎么编？

#include<stdio.h>

bool GetCharge(int Sum,int Money);
void Getsmalcharge(int Money,int *ChargeNum);
void main()
{
char state='N';
int Sum=0;
char Pro;
printf("\n********************************\n");
while(true)
{
state='N';
Sum=0;
while(state=='N'||state=='n')
{
printf("\n输入购买物品(a,b,c):");
scanf("%c",&Pro);
getchar();
switch(Pro)
{
case 'a':
Sum=Sum+1;
break;
case 'A':
Sum=Sum+1;
break;
case 'b':
Sum=Sum+5;
break;
case 'B':
Sum=Sum+5;
bre