Task planning

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The Task Scheduler (formerly Task Scheduler ) is a component of all modern versions of Microsoft Windows and allows you to launch applications time or recurring at set times.

precursor

The forerunner of the task planning was the schedule service (or from Windows NT 4.0 under the English term Schedule ) called system service, which was originally part of the LAN Manager and was later adopted in Windows NT 3.1 and all subsequent versions. The service could only be AT.EXEcontrolled via the command line program. It was originally designed to start background applications regularly (e.g. creating a backup), which is why it had certain restrictions; the executed programs could not communicate with the user in any way (unless the parameter was /INTERACTIVEtransferred), the applications did not appear in the task manager and the termination of a program started in this way required the entire computer to be restarted. If AT.EXEa network drive was connected without being subsequently disconnected, the network drive was visible to all users, but could only be disconnected again by administrators via the command line.

The syntax of AT.EXEwas changed between Windows NT 3.51 and Windows NT 4.0, for example to allow file names and paths with spaces to be passed as parameters. An entry in the Windows registry can be used to force the old syntax to be used to fix compatibility problems with older scripts. This setting has only been retained since Service Pack 4 and is not deleted after each system start.

Task planning 1.0

The original form of today's task planning appeared under the name "Planned Tasks" initially as part of the Plus! -Package for Windows 95 , later it was in a revised form as an optional component part of Internet Explorer 4.0 and thus available for Windows 95 and Windows NT 4.0, whereby the existing schedule service was replaced if necessary. All later versions of Windows, in which Internet Explorer was already integrated, also included the task scheduler. The task planning ran as a system service in the background (or under Windows 9x as an executable file MSTASK.EXE) and enabled applications to be started to be entered and deleted via a virtual folder “Planned Tasks”. A command line program to control the service was initially missing, but the old command AT.EXEremained functional (even if tasks added with AT were incompatible with those in the “Planned Tasks” folder). Only from Windows XP, there was the new command line utility schtasks, which AT.EXEhas been replaced; for reasons of compatibility, however, AT is still included in today's versions of Windows. The problem is that the parameters of the command have been schtaskstranslated into the individual language versions of Windows, so scripts cannot be ported between different language Windows systems. Programmers were able to control and manipulate the task planning via COM objects. From Windows 2000 the service was called "Task Scheduler".

Individual tasks were stored in the Windows registry database under Internet Explorer 4.0. Instead, Internet Explorer 5.0 saves tasks as files with the file extension .JOBon the hard drive.

Task planning 2.0

With Windows Vista the "task planning" got its current name and was completely redesigned and redesigned. The most important innovations are:

  • Task planning is integrated in the Microsoft Management Console and can be called up via an MMC applet; the old folder “Planned Tasks” is no longer available. Individual tasks are saved as XML files and can therefore be edited in any text editor.
  • Tasks can no longer be started just once at a specific time or recurring at regular intervals, but also depending on a specific event (e.g. entry in the event log , no user activity)
  • Several applications to be started can also be combined in one task, which are then executed one after the other
  • You can also define what should happen if a task fails.
  • The API for accessing the task scheduler has been significantly expanded, but there is no way to access it via .NET . PowerShell 3.0 or later has cmdlets for creating and modifying tasks.

Web links

Individual evidence

  1. Microsoft Knowledge Base - Q121562: Applications Started with AT Are Not Interactive
  2. Microsoft Knowledge Base - Q138340: Trouble Quitting Program Started with AT.EXE Scheduler
  3. Microsoft Knowledge Base - Q103650: Network Connections Made with the AT Command are Persistent
  4. Microsoft Knowledge Base - Q177651: Windows NT 4.0's AT Command Handles Quotation Marks Differently Than Windows NT 3.51
  5. Microsoft Knowledge Base - Q196731: Application That Requires Schedule Service Fails
  6. Microsoft Knowledge Base - Q220149: AT Tasks Cannot Be Viewed Using the Task Scheduler Tool
  7. Description of the SCHTASKS command
  8. Microsoft Knowledge Base - Q279830: Internet Explorer May Not Convert Jobs to Task Scheduler Jobs When You Upgrade to Internet Explorer 5
  9. About Scheduled Jobs - Windows PowerShell