The Rooms system  uses multiple virtual workspaces, where the overlapping window strategy is used in each of these single-screen workspaces. Each task is devoted to a workspace, where users can switch to other tasks using either the overview or the doors between workspaces for rapid transitions. Basically, the Rooms system tries to overcome the problems due to the increase in the number of windows by increasing the total screen space, by introducing multiple virtual workspaces, and by techniques which allow fast switching between workspaces. Also, it allows users to organize tasks into workspaces, where all windows belonging to a single task exist. Windows belonging to a task are restricted to fit in a single screen. Although it is possible to partition tasks into subtasks and place each subtask in different workspaces and utilize doors for efficient transitions between these workspaces, users can easily lose task context since information for a task is distributed to multiple screens. There is no mechanism which allows multi-window operations. Tasks are restricted to fit in a two-level hierarchy: the overview level, and the workspace level.
The Cedar  system also uses tiling, where windows are organized in two columns of arbitrary number of windows. It also uses space-filling tiled layout, but proportional resizing is not provided. Windows can not be grouped hierarchically and multiple window operations are not provided. Windows minimized are iconized at the bottom of the desktop, possibly causing disorientation if the number of windows is high.
The Dylan programming environment uses a pane-based window system , which allows both horizontal and vertical panes, with a mechanism to create links between panes. The Dylan programming environment does not support multiple window operations and hierarchical organization of windows.
Xerox/Star , RTL/CRTL [8, 9], and Windows 1.0 also used tiling, but hierarchical organization and multiple operations were not provided. CIWM  uses automated window management. Although automatic strategies in window management relieve the burden of window management, direct user control is preferable as in most HCI artifacts. Myers has an excellent taxonomy of these early windowing systems .