Describe what a handle is with respect to an object and list three objects within the Windows operation system? Solution A handle is with respect to an object: Handle: In any operating system, real pointers are still opaque handles into the virtual memory space of the process, which enables the O/S to manage and rearrange memory without invalidating the pointers within the process. A real pointer may be given as the handle when the API writer intends that the user of the API be insulated from the specifics of what the address returned points to; in this case it must be considered that what the handle points to may change at any time . Object: An object is a data structure,it represents a system resource, such as a file, thread, or graphic image. An application cannot directly access object data or the system resource that an object represents. Instead, an application must obtain an object handle, which it can use to examine or modify the system resource. Each handle has an entry in an internally maintained table. These entries contain the addresses of the resources and the means to identify the resource type. About Handles and Objects: The system uses objects and handles to regulate access to system resources for these two reasons. 1. The use of objects ensures that Microsoft can update system functionality, as long as the original object interface is maintained. When subsequent versions of the system are released. 2.The use of objects are advantage of Windows security. Each object has its own access-control list (ACL) that specifies the actions a process can perform on the object. The system examines an object\'s ACL each time an application creates a handle to the object. The system provides three categories of objects: 1.User 2.graphics device interface (GDI) and 3.kernel. 1.User: The system uses user objects to support window management. User objects: Accelerator table:Keyboard Accelerators, Caret:Carets, Cursor:Cursors, DDE conversation:Dynamic Data Exchange Management Library, Hook:Hooks, Icon:Icons, Menu:Menus, Window:Windows, Window position:Windows. 2.graphics device interface (GDI) : GDI objects to support graphics. Bitmap:Bitmaps, Brush:Brushes DC:Device Contexts Enhanced metafile:Metafiles Enhanced-metafile DC:Metafiles Font:Fonts and Text Memory DC:Device Contexts Metafile:Metafiles Metafile DC:Metafiles Palette:Colors Pen and extended pen:Pens Region:Regions 3.kernel. kernel objects to support memory management, process execution, and interprocess communications (IPC). Access token: Access control Change notification:Directory change notifications Communications device: communications job: job objects desktop:desktops event:synchronization file\"files and clusters pipe:pipes process:processes and threads thread: processes and threads timer:synchronization timerque:synchronization windowstation:window stations Handle and Object Functions: close handle - Closes an open object handle. Duplicate handle - Duplicates an object handle .