Introduction
AmigaOS 4.0 uses a GUI system based around Intuition, which is a set of software routines that all Amiga developers can use to create a consistent interface for the user across the range of Amiga applications. When you boot into AmigaOS 4.0 you are located at the 'Workbench' screen, akin to the Desktop on a Mac and Linux, and 'My Computer' when running MSWindows.

Opening a Window
In our example above, the OS4 disk has been opened and its contents are displayed within a window. At the top left hand corner of the window is the 'close gadget' - clicking on this will close the window. From there, the next image to the right is the 'zoom gadget' - this can be used to shrink/expand the size of the window. Next to that, at the top right hand corner is the 'depth gadget' - this is used to move the window to the front or push it behind any other open windows. At the bottom right hand corner is the 'sizing gadget' - this can be used to drag the corner of the window to resize it. Down the right hand side and along the bottom are two 'scroll gadgets' - these are used to scroll the contents up/down and left/right respectively within the window.

Apart from the 'disk icons' that we have already seen, the are several other icon types. In our example above, you can see 'drawer icons' that are the equivalent of folders or directories, and 'project icons' that are equivalent of application files but with AmigaOS 4.0 they do not need to have a special suffix as part of the name so that it can identify the associated program, e.g. 'example.jpg' can simply be 'example'. You can either explicitly name the associated program within the icon information, or AmigaOS 4.0 will interrogate the file and automatically determine the program. There is another icon type not shown here and that is the 'tool icon' used to identify programs.

AmiDock
AmiDock, shown at the bottom of the screen, is used to run frequently used programs and can be customised in a variety of ways by the user, and provides sub-docks for easy classification of programs. AmiDock is discussed in more detail in the Workbench section.

Special Amiga Keys
Those familiar with the classic Amiga keyboard will know that it has two special keys:

- Left Amiga located to the left of the space bar and drawn in solid colour
- Right Amiga located to the right of the space bar and drawn in outline

Accessing Pull-Down Menus
Most programs, including the 'Workbench' have pull-down menus, which you can access by pressing the right mouse button - unlike some other systems you do not need to move the mouse pointer to the top of the screen before activating - it works anywhere. In these menus you may see 'hot keys' which are the keyboard equivalents of the menu items, and in most cases they will show as a large A with a character next to it as shown. This corresponds to the Right Amiga key (right Windows key) plus the character shown - in this case Right Amiga - B toggles the backdrop of the Workbench screen.

Other Useful Key Combinations
In addition to the key combinations shown in the pull-down menus, there are some for resizing windows that are not so readily known, for example:

• If you click on the zoom gadget, the window normally toggles between the 'snapshot' size and a small (shrunk) window. If you hold down the shift key while clicking on the zoom gadget, the window will zoom to a full-screen window. After doing this you will that clicking on the zoom gadget now toggles between full-screen and the normal 'snapshot' size for that window. However, the window may be moved or resized to change its zoomed or original position using the other gadgets.
• If you click on the sizing gadget, an outline of the window appears which can be dragged from the gadget to define the new size and shape of the window, and the window changes to this size when the selection button is released. However, the redraw operation can be cancelled by pressing the menu button before releasing the selection button.
• If you simply want to change the shape of the window, you can hold down the Ctrl and Left Amiga buttons and drag the window borders instead.

Screens and Screen Dragging
A screen is an area of the monitor display with a given display mode and set of properties, including the resolution, size and number of colours. Different display modes may be used for different purposes, and if necessary the screen size can be larger than the viewable area on the monitor. The Workbench screen, as shown above, is the first screen displayed after the AmigaOS boots. All windows open within a screen, for example the OS4 window shown above has been opened on the Workbench screen.

The AmigaOS permits several screens to be open at any given time. New screen normally open on top of other screens, covering them. To view and access screens that are covered by others, you can either drag the frontmost screen down or use gadgets or keyboard shortcuts to depth-arrange them. When working with screens, here are some helpful hints:

• Left Amiga + m can be used to page through open screens.
• Left Amiga + n can be used to return to the Workbench screen, regardless of how may other screen are open.
• Items cannot be dragged between screens, although the mouse pointer moves freely from screen to screen.
• Only one window on one screen at a time can accept keyboard or mouse input.
• Most screens have a title bar that you can use to move them by positioning the pointer over the title bar, holding down the left mouse button and dragging the mouse down the screen.
• For a screen with no title bar (although this works with a title bar as well) simply hold down the Left Amiga key, position the pointer anywhere on the screen, hold down the left mouse button and drag the mouse down the screen.
• Where a screen is larger than the monitor's display area, you can scroll the unseen areas of the screen into view when you move the pointer to the edges of the viewable area.
• A screen cannot be dragged so that the bottom of the screen rises above the bottom of the monitor display.
• In addition to the basic dragging options described above, the AmigaOS also provides 'alternate drag settings' which enables a screen to be dragged in any direction.

  Shift Key (either)	switches to and from the alternate drag settings for a single screen dragging operation. You can release the qualifier after each swap; the new drag settings stick around until the end of the dragging operation, or until the next time the qualifier is pressed again during the same dragging operation.
  Middle mouse button	same functionality as Shift Key. You can use this if Shift was chosen as a qualifier for screen meta dragging (in which case it won't swap drag settings).
  Left Amiga + a	switches to and from the alternate screen drag settings in a persistent way (that is, until the next time you select this command key combination). Note that as long as there are screens in an "illegal" position for the current screen drag settings, you will still be able to move them as if the other set of drag settings were in use for them; such screens will only start honoring the current drag settings once they've been left in a "legal" position at the end of a dragging operation.