这个我是真的不懂

#include<stdio.h>
main()
{int x,y,z;
scanf("%d%d",&x,&y);
z=area(x,y);
printf("area is %d\n",z);
}
int area(int a,int b)
{int c;
c=a*b;
return(c);
}
为什么会粗现
--------------------Configuration: 2312 - Win32 Debug--------------------
Compiling...
2312.cpp
D:\Microsoft Visual Studio\MyProjects\2312\2312.cpp(5) : error C2064: term does not evaluate to a function
D:\Microsoft Visual Studio\MyProjects\2312\2312.cpp(7) : warning C4508: *main* : function should return a value; *void* return type assumed
执行 cl.exe 时出错.


2312.exe - 1 error(s), 0 warning(s)

求大神解答！！！

#include<stdio.h>
main()
{int x,y,z;
printf("请输入两个正整数: \n");


scanf("%d,%d",&x,&y);
z=area(x,y);
printf("area is %d\n",z);
}
int area(int a,int b)
{
int c;
c=a*b;
}

#include<stdio.h>
int area(int a,int b);
void main()
{
int x,y,z;


scanf("%d%d",&x,&y);


z=area(x,y);
printf("area is %d\n",z);


}


int area(int a,int b)
{
int c;
c=a*b;
return c;
}