In O, everything drawn on the screen belongs to an object. This
can be a molecular object, a skeleton object, an electron density object
and so on. For each object generated, a minor menu in one of the five major
menus called Object_1, _2, _3, _4, and _5
is renamed. If an object
called mol_a is created, then the new minor menu name would be
^mol_a. Objects can be switched on or off by picking these names on
the screen, or by typing them on the keyboard. Thus, typing
^mol_a
at the terminal toggles the display state of the object called mol_a.
Some objects are created explicitly by the user, while other objects are created by commands. For example, the command Move_zone will create an object called fragmv_rt. Therefore, while this command is active, you will be able to switch the moving object on or off. The names of the minor menus are not always updated each time a new object is created, but activating the command On_off will place the names of all currently active objects in the five major menus and display them on the screen.
Some objects, such as atomic objects, are pickable. This allows atoms to be identified. Other objects are not pickable. These include electron density maps and objects created using O graphic object descriptors (see Chapter 7) and displayed with the Draw_object command.