Question

C语言疑问： 出现warning C4013: 'add' undefined; assuming extern returning int 怎么解决啊 ~ 谢谢啦

#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int count=0,ok=0,a,b;
void main()
{
int x,y,op,end=0;
srand(time(NULL));
printf("\n***** 这是一个加减法运算的小游戏，回答为 999 表示程序结束 *****\n");
while(end!=999)
{
op=rand()%2;
x=1+rand()%99;
y=1+rand()%99;
a=add(x,y);b=minus(x,y);
end=(op==0)?a:b;

}
printf("\n");
}

int add(int x,int y)
{
int answer; long accuracy;
printf("\n %d+%d=",x,y);
scanf("%d",&answer);
while(answer!=999){
if(answer==(x+y)){ count++;ok++;accuracy=(ok/count)*100;
printf(" 回答正确!\n您总共回答了%d道题，答对%d道题，答对率为%.2f%。\n",count,ok,accuracy);return 1;}
else {count++;accuracy=(ok/count)*100;
printf(" 回答错误!\n您总共回答了%d道题，答对%d道题，答对率为%.2f%。\n",count,ok,accuracy);
return 1;}
}
return 999;}

int minus(int x,int y)
{
int answer; long accuracy;
printf("\n %d-%d=",x,y);
scanf("%d",&answer);
while(answer!=999){
if(answer=(x-y)){ count++;ok++;accuracy=(ok/count)*100;
printf(" 回答正确!\n您总共回答了%d道题，答对%d道题，答对率为%.2f%。\n",count,ok,accuracy);return 1;}
else {count++;accuracy=(ok/count)*100;
printf(" 回答错误!\n您总共回答了%d道题，答对%d道题，答对率为%.2f%。\n",count,ok,accuracy);
return 1;}
}

Answer 1

你得在main前面声明函数或者把你的函数写在main的前面
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int count=0,ok=0,a,b;
int add(int x,int y)；
int minus(int x,int y)；
void main()