四则运算的程序

#includestdio.h
#includemath.h
#includewindows.h
int right=0;
int wrong=0;
void add()
{
int a,b,c;
a=rand()%100;
b=rand()%100;
printf("请回答：\n\t\t %d + %d = ",a,b);
scanf("%d",c);
if(a+b==c)
{
printf("回答正确!\n");
right++;
}
else
{
printf("回答错误!\n");
wrong++;
}
}
void minu()
{
int a,b,c;
a=rand()%100;
b=rand()%100;
printf("请回答：\n\t\t %d - %d = ",a,b);
scanf("%d",c);
if(a-b==c)
{
printf("回答正确!\n");
right++;
}
else
{
printf("回答错误!\n");
wrong++;
}
}
void mul()
{
int a,b,c;
a=rand()%100;
b=rand()%100;
printf("请回答：\n\t\t %d * %d = ",a,b);
scanf("%d",c);
if(a*b==c)
{
printf("回答正确!\n");
right++;
}
else
{
printf("回答错误!\n");
wrong++;
}
}
void di()
{
int a,b,c;
a=rand()%100;
b=rand()%100;
printf("请回答：\n\t\t %d / %d = ",a,b);
scanf("%d",c);
if(a/b==c)
{
printf("回答正确!\n");
right++;
}
else
{
printf("回答错误!\n");
wrong++;
}
}
void main()
{
int choise;
int con=0;
printf("\n\t\t\t欢迎进入小学简易四则运算\n\n");
while(1)
{
printf("请选择：\n");
printf("\t\t\t 加法运算（请输入1）\n");
printf("\t\t\t 减法运算（请输入2）\n");
printf("\t\t\t 乘法运算（请输入3）\n");
printf("\t\t\t 除法运算（请输入4）\n");
printf("\t\t\t 退出运算（请输入5）\n");
if(con==0)
scanf("%d",choise);
switch(choise)
{
case 1:
add();
break;
case 2:
minu();
break;
case 3:
mul();
break;
case 4:
di();
break;
case 5:
return;
}
printf("\n\t\t\t继续运算？（请输入1）\n");
printf("\n\t\t\t重新选择？（请输入2）\n");
printf("\n\t\t\t退出运算？（请输入3）\n");
scanf("%d",con);
if(con==1)
con=1;
else if(con==2)
con=0;
else if(con==3)
break;
else
printf("抱歉!，你输入的指令有误!请重新输入!\n");
}
printf("您总共完成了 %d 道题\n正确 %d 道\n错误 %d 道\n",right+wrong,right,wrong);
}