Task Manager is one of the most widely used apps, and it has a long history. It showed up in early versions of Windows as a simple utility to close and switch between programs, and has had functionality added to it through several releases to make it what it is today.
Figure 1: Windows 3.0 Task List
Figure 2: Windows NT 4.0 Task Manager (now with “new task”)
Figure 3: Windows XP Task Manager (with new Networking and Users tabs)
Windows 8 Task Manager
Read the extensive blogpost on thye new taskmanager, explaining the heatmap, friendlynames and more: