define global variable in c programhow to define

Question

Define global variable in c++ program:

How to define a global variable and need of global variable in c++ program.

int main()

{

   int m=20;

   clrscr();

   for( int i=0;i<4;i++)

   {

     m=60;

     cout << m;

     cout<<"the global variable is\n"<

   }

     getch();

return m;

}