#include?<stdio.h>
float?price(int?dictance,int?useTime)
{
???int?startPrice?=?13;
???float?fuel?=?1;
???float?milePrice?=?2.3;
???float?totalPrice;
???while(useTime<5||useTime>=23)
???{
???????if(useTime<0||useTime>24)
???????{
???????????printf("%s\n","時間輸入有誤。");
???????????return?0;
???????????break;
???????}
???????else
???????{
???????????milePrice*=1.2;
???????????break;
???????}
???}
???if(distance<=3)
???{
???????totalprice?=?startPrice+fuel;
???}
???else
???{
???????totalPrice?=?startPrice+milePrice*(dictance-3)+fuel;
???}
???return?totalPrice;
}

int?main()
{
???int?amTime?=?9;
???int?pmTime?=?18;
???int?distance?=?12;
???printf("小明上午打車的費用是%f\n",price(distance,amTime));
???printf("小明下午打車的費用是%f\n",price(distance,pmTime));
???printf("小明打車的總費用是%f\n",price(distance,amTime)+price(distance,pmTime));
???return?0;
}

運行結果如下：

/249/5642/CD9l/hello.c: In function 'price':
/249/5642/CD9l/hello.c:22:8: error: 'distance' undeclared (first use in this function)
? ? if(distance<=3)
? ? ? ?^
/249/5642/CD9l/hello.c:22:8: note: each undeclared identifier is reported only once for each function it appears in
/249/5642/CD9l/hello.c:24:9: error: 'totalprice' undeclared (first use in this function)
? ? ? ? totalprice = startPrice+fuel;