function should return a value; 'void' return type assumed

#include<iostream>using namespace std;void sphere();int main(){sphere();//return 0;}void sphere(){double radius;cout<<"Please input radius:";cin>>radius;if (radius<0) return;cout<<"The result is "<<radius*radius*3.14*4<<"/n";//return 0;}

--------------------Configuration: ex - Win32 Debug--------------------
Compiling...
ex01.cpp
D:/960174/My Documents/VC/ex/ex01.cpp(8) : warning C4508: 'main' : function should return a value; 'void' return type assumed
Linking...

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

 

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有返回值的函数无任在任何条件下都必须有返回值,