Hai,
Is it possible to create a 3D square where the vertices of the square should be given during the execution of the program?
B’coz the size of the object should vary whenever i want.
with Thanks…
Sure, just pass in variables to glVertex3f, and hook up the variables to the input of your choice. Check out GLUT for keyboard input, for instance.
(Mind you, OpenGL does drawing only - everything else is your problem. 
)