错很多，求大神求解

Question

# include <stdio.h>int main () int sum;    int a; double pai=3.14;printf("请输入a的值");scanf("%d",&a);{    void action1(int),action2(int,int),action3(int); int bianhao;    scanf("%d",&bianhao); printf("请选择编号：1，正方形；2，长方形；3，圆形；"); switch(bianhao) { case '1':action1(a);break; case '2':action2(a);break; case '3':action3(a);break; default:printf("enter datd error"); } return 0;}void action1(int x){ printf("sum=a*a%d\n",sum);}void action2(int x,int y){ printf("sum=x*y%d\n",sum);}void action3 (int r){ printf("sum=pai*r*r%d\n",sum);}

Answer 1

为什么不拿起一本C语言的教学书照着代码敲？感觉楼主对基本的语法完全不清楚啊

Answer 2

main函数的大括号，你写到哪里去了