Visual C++ :: OpenGL - 2D Movement With Respond To Keypress

I'm trying to implement keyboard controls to move a sphere(Player) with respond to keypress. Currently, when I press any key my character will move to the right by 0.1. How can I move my character with w(up),a(left),s(down),d(right) in their respective directions using respond to keypress?

Code:
class Player {
private:
double x, y;
public:
Player(double a, double b){x=a;y=b;}
void respondtokeypress(char a)

[Code] ....