تحديث Windows 7
Ashlie Hagenson
To make sure you're protected by the latest security updates, Google Chrome can automatically update when a new version of the browser is available on your device. With these updates, you might sometimes notice that your browser looks different.
The browser saves your opened tabs and windows and reopens them automatically when it restarts. Your Incognito windows won't reopen when Chrome restarts. If you'd prefer not to restart right away, click Not now. The next time you restart your browser, the update will be applied.
Windows Update is a Microsoft service for the Windows 9x and Windows NT families of the Microsoft Windows operating system, which automates downloading and installing Microsoft Windows software updates over the Internet. The service delivers software updates for Windows, as well as the various Microsoft antivirus products, including Windows Defender and Microsoft Security Essentials. Since its inception, Microsoft has introduced two extensions of the service: Microsoft Update and Windows Update for Business. The former expands the core service to include other Microsoft products, such as Microsoft Office and Microsoft Expression Studio. The latter is available to business editions of Windows 10 and permits postponing updates or receiving updates only after they have undergone rigorous testing.
As the service has evolved over the years, so has its client software. For a decade, the primary client component of the service was the Windows Update web app that could only be run on Internet Explorer. Starting with Windows Vista, the primary client component became Windows Update Agent, an integral component of the operating system.
The service provides several kinds of updates. Security updates or critical updates mitigate vulnerabilities against security exploits against Microsoft Windows. Cumulative updates are updates that bundle multiple updates, both new and previously released updates. Cumulative updates were introduced with Windows 10 and have been backported to Windows 7 and Windows 8.1.
Microsoft routinely releases updates on the second Tuesday of each month (known as the Patch Tuesday), but can provide them whenever a new update is urgently required to prevent a newly discovered or prevalent exploit. System administrators can configure Windows Update to install critical updates for Microsoft Windows automatically, so long as the computer has an Internet connection.
In Windows 10 and Windows 11, the use of Windows Update is mandatory, however, the software agreement states that users may stop receiving updates on their device by disconnecting their device from the Internet.[1][2]
Windows Update was introduced as a web app with the launch of Windows 98 and offered additional desktop themes, games, device driver updates, and optional components such as NetMeeting.[3] Windows 95 and Windows NT 4.0 were retroactively given the ability to access the Windows Update website and download updates designed for those operating systems, starting with the release of Internet Explorer 4. The initial focus of Windows Update was free add-ons and new technologies for Windows. Security fixes for Outlook Express, Internet Explorer and other programs appeared later, as did access to beta versions of upcoming Microsoft software, e.g. Internet Explorer 5. Fixes to Windows 98 to resolve the Year 2000 problem were distributed using Windows Update in December 1998. Microsoft attributed the sales success of Windows 98 in part to Windows Update.[4]
The Windows Update web app requires either Internet Explorer or a third-party web browser that supports the ActiveX technology. The earliest version of the web app, version 3, does not send any personally-identifiable information to Microsoft. Instead, the app downloads a full list of every available update and chooses which one to download and install. But the list grew so large that the performance impact of processing became a concern. Arie Slob, writing for the Windows-help.net newsletter in March 2003, noted that the size of the update list had exceeded 400 KB, which caused delays of more than a minute for dial-up users.[5] Windows Update v4, released in 2001 in conjunction with Windows XP, changed this. This version of the app makes an inventory of the system's hardware and Microsoft software and sends them to the service, thus offloading the processing burden to Microsoft servers.[5]
Critical Update Notification Utility (initially Critical Update Notification Tool) is a background process that checks the Windows Update web site on a regular schedule for new updates that have been marked as "Critical". It was released shortly after Windows 98.
By default, this check occurs every five minutes, plus when Internet Explorer starts; however, the user could configure the next check to occur only at certain times of the day or on certain days of the week. The tool queries the Microsoft server for a file called "cucif.cab", which contained a list of all the critical updates released for the operating system. The tool then compares this list with the list of installed updates on its machine and displays an update availability notification. Once the check is executed, any custom schedule defined by the user is reverted to the default. Microsoft stated that this ensures that users received notification of critical updates in a timely manner.[6]
An analysis done by security researcher H. D. Moore in early 1999 was critical of this approach, describing it as "horribly inefficient" and susceptible to attacks. In a posting to BugTraq, he explained that, "every single Windows 98 computer that wishes to get an update has to rely on a single host for the security. If that one server got compromised one day, or an attacker cracks the [Microsoft] DNS server again, there could be millions of users installing trojans every hour. The scope of this attack is big enough to attract crackers who actually know what they are doing..."[7]
Unlike its predecessor, Automatic Updates can download and install updates. Instead of the five-minute schedule used by its predecessor, Automatic Updates checks the Windows Update servers once a day. After Windows Me is installed, a notification balloon prompts the user to configure the Automatic Updates client. The user can choose from three notification schemes: Being notified before downloading the update, being notified before installing the update, or both. If new updates are ready to be installed, the user may install them before turning off the computer. A shield icon will be displayed on the Shutdown button during this time.
Windows XP and Windows 2000 SP3 include Background Intelligent Transfer Service, a Windows service for transferring files in the background without user interaction. As a system component, it is capable of monitoring the user's Internet usage, and throttling its own bandwidth usage in order to prioritize user-initiated activities. The Automatic Updates client for these operating systems was updated to use this system service.
Automatic Updates in Windows XP gained notoriety for repeatedly interrupting the user while working on their computer. Every time an update requiring a reboot was installed, Automatic Updates would prompt the user with a dialog box that allowed the user to restart immediately or dismiss the dialog box, which would reappear in ten minutes; a behavior that Jeff Atwood described as "perhaps the naggiest dialog box ever."[8]
In 2013, it was observed that shortly after the startup process, Automatic Updates (wuauclt.exe) and Service Host (svchost.exe) in Windows XP would claim 100% of a computer's CPU capacity for extended periods of time (between ten minutes to two hours), making affected computers unusable. According to Woody Leonhart of InfoWorld, early reports of this issue could be seen in Microsoft TechNet forums in late May 2013, although Microsoft first received large number of complaints about this issue in September 2013. The cause was an exponential algorithm in the evaluation of superseded updates which had grown large over the decade following the release of Windows XP. Microsoft's attempts to fix the issue in October, November and December proved futile, causing the issue to be escalated to the top priority.[9][10]
Starting with Windows Vista and Windows Server 2008, Windows Update Agent replaces both the Windows Update web app and the Automatic Updates client.[11][12] It is in charge of downloading and installing software update from Windows Update, as well as the on-premises servers of Windows Server Updates Services or System Center Configuration Manager.[13][14]
Windows Update Agent can be managed through a Control Panel applet, as well as Group Policy, Microsoft Intune and Windows PowerShell. It can also be set to automatically download and install both important and recommended updates. In prior versions of Windows, such updates were only available through the Windows Update web site. Additionally, Windows Update in Windows Vista supports downloading Windows Ultimate Extras, optional software for Windows Vista Ultimate Edition.
Unlike Automatic Updates in Windows XP, Windows Update Agent in Windows Vista and Windows 7 allows the user to postpone the mandatory restart (required for the update process to complete) for up to four hours. The revised dialog box that prompts for the restart appears under other windows, instead of on top of them. However, standard user accounts only have 15 minutes to respond to this dialog box. This was changed with Windows 8: Users have 3 days (72 hours) before the computer reboots automatically after installing automatic updates that require a reboot. Windows 8 also consolidates the restart requests for non-critical updates into just one per month. Additionally, the login screen notifies them of the restart requirements.[15]
Windows Update Agent makes use of the Transactional NTFS feature introduced with Windows Vista to apply updates to Windows system files. This feature helps Windows recover cleanly in the event of an unexpected failure, as file changes are committed atomically.[16]
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