The New Task Scheduler (Windows 95 and Windows NT 4.0)
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Archived content - No warranty is made as to technical accuracy. Content may contain URLs that were valid when originally published, but now link to sites or pages that no longer exist.
This paper is intended for software developers and system integrators. It describes the Task Scheduler, a new service and user interface that runs on both the Microsoft® Windows® 95 and Windows NT® operating systems. Task Scheduler is accessible from the same programming interfaces whether you are adding scheduling services to a program running under Windows NT or Windows 95.
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Why Do We Need Another Scheduler?
Every new system or application offers some kind of scheduling service, something that automatically invokes scripts or programs at specified times. The most common, and in many ways the least useful, is the StartUp program group, present in all of the Windows operating systems. The problem with the StartUp group and all the other schedulers is that they are all designed for different needs and are rarely built to integrate with all the components in a system, or work seamlessly in more than one system. The Windows 95 Plus! Pack provided the System Agent which included a user interface as well as a set of application programming interfaces (APIs). Windows NT came with the AT command, not an especially user-friendly tool that required a fair amount of familiarity with the arcane world of the command prompt. Many applications provide a place for users to configure some scheduling mechanism for performing recurring, necessary maintenance tasks. None of these schedulers work well together, and few provide any programmable interfaces.
A Common, Flexible, and Extensible Interface
Task Scheduler provides a friendly user interface1 that is the same one on both Windows 95 and Windows NT, with the exception of added security features in Windows NT. The interface is fully integrated into the operating system, and is accessible from the My Computer icon on your desktop. Users can drag-and-drop programs right into Task Scheduler to quickly add a new task or use the provided "Create Scheduled Task" wizard.
You can schedule any script, program, or document to be invoked at any time or any interval, every day to once a year, and on events like system boot, user logon, or system idle. A task is saved as a file with a .job extension, which enhances the ability to move from computer to computer. Administrators can create scheduled maintenance task files and place them where needed. You can access the Task Folder remotely from the Network Neighborhood as well as send tasks in e-mail.
On Windows NT, scheduled tasks are created and executed based on standard Windows NT security permissions. Tasks are persisted as files and are configurable by Windows NT File System (NTFS) access control lists (ACLs) to set who can view, delete, modify, or use them. The items that make up the task, the scripts, programs, and documents, are also still controlled by whatever ACLs are present. Under Windows NT, this provides a high degree of control over how files are accessed.
Note: When you move a .job file on a Windows NT system, a user's credentials will not transfer with the file. They must be reentered after moving the file. This is because the credentials are not stored with the task, but by the security system of Windows NT.
Since Windows NT is a multiuser environment, when tasks are created, a user name and password are required that will set the current security context in which the task will execute. This allows multiple tasks to run on a single computer in the security context that was supplied. Multiple users can each have their own individual scheduled tasks.
Why Should Developers Be Interested?
Task Scheduler provides a common and fully programmable set of interfaces. Task Scheduler is a COM-based object, which adds all the advantages of COM, including language and platform independence (as well as remote capabilities provided by DCOM). If you are developing an application to run under both Windows 95 and Windows NT, you can write to the same interfaces regardless of the platform.
All of the functionality in Task Scheduler is completely accessible from these APIs. This means you don't have to "rewrite the wheel" when you want to add scheduling services to your applications. You can be assured that the scheduling services will already be there in the operating system and that they'll be robust, stable, and, over subsequent releases, more feature-rich.
Finally, with Task Scheduler you don't even have to write your own scheduling property pages. You can invoke Task Scheduler's property pages from the same APIs. You can create the property pages and dialog boxes that are specific to your application and then invoke Task Scheduler's property pages as needed.
So, How Do I Get It?
Task Scheduler will be shipped along with the next major releases of Windows (code-named "Memphis"), Windows NT, and Microsoft Internet Explorer. The Task Scheduler user interface is currently available in Internet Explorer 4.0 beta 1 and the Platform SDK are documented in the Internet SDK client at http://www.microsoft.com/msdn/sdk.
The goal of the Task Scheduler team is to unify a set of disparate tools to make a user's experience more consistent and satisfying. By providing common APIs across platforms, Microsoft hopes to help developers in building their applications and adding scheduling services—virtually for free. Robust, cross-platform, flexible scheduling is one less thing you have to create from scratch.
For More Information
For the latest information on Windows 95 check out our World Wide Web site at www.microsoft.com/windows.
For the latest information on Windows NT Server, check out our World Wide Web site at http://www.microsoft.com/ntserver or the Windows NT Server Forum on the Microsoft Network (GO WORD: MSNTS).
The information contained in this document represents the current view of Microsoft Corporation on the issues discussed as of the date of publication. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information presented after the date of publication.
This White Paper is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN THIS DOCUMENT.
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|1||The item that is different at this time is that Win9X has an idle trigger. This will be the same with the release of Windows NT version 5.0.|