Data member placement in a class. Where to place and what is the importance of that placement ?

Question

Class c1 | class c1 | class c1
{ | { | {
int a =10; | public : | public:
public: | int a=10; | void main()
void display() | void display() |{
{ | { | cin>>a;
cout<<a; | cout<<a; | cout<<a;
} | } | }
} | } |