When i am trying to compile this with gcc it's saying "undefined refer

#include
int main(){
return 0;}

When i am trying to compile this with gcc it's saying "undefined reference ". But when i am using g++ it is working. Can anyone help me to solve this so that i can use gcc???? I used gcc before . But suddenly it is not working. I have tried with other header files like vector algorithm. They are fine.  But when i am using iostream gcc isn't working with it.