调用函数求三个数中的最大数

#include<stdio.h>int main(){int max();extern int A,B,C;  //把外部变量A,B,C的作用域扩展到从此处开始printf("please input three integer numbers:\n");scanf("%d%d%d",&A,&B,&C);printf("max=%d\n",max());return 0;}int A,B,C;     //定义外部变量A,B,Cint max(){int m;m=(A>B)?A:B;if(m<C){m=C;}return m;}