The Fc.exe command does not work correctly in Windows Vista or in Windows Server 2008 when the command compares files that differ at every 128th byte of a character string

On a computer that is running Windows Vista or Windows Server 2008, you use the Fc.exe command to compare two files. If the two files both contain a character string that has more than 128 bytes, the Fc.exe command may not check the character at every multiple of 128. Therefore, when you use the Fc.exe command to compare the files that differ only at the 128th byte, the 256th byte, the 384th byte, and so on, the Fc.exe command will find no differences. This result is incorrect.

For example, assume that you have two files that contain a character string of 200 bytes. Also assume that only the character at the 128th byte differs from one file to the other. When you use the Fc.exe command to compare the two files, the command does not display the differences between the two files, and you receive the following output:

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.

Prerequisites

No prerequisites are required.

Restart requirement

You do not have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.

Windows Vista and Windows Server 2008 file information notes

• The files that apply to a specific product, milestone (RTM, SPn) can be identified by examining the file version numbers as shown in the following table:
  Collapse this tableExpand this table

  Version	Product	Milestone	Service branch
  6.0.600 0. 20 xxx	Windows	RTM	LDR
  6.0.600 1. 22 xxx	Windows Vista SP1 and Windows Server 2008 SP1	SP1	LDR

• Service Pack 1 is integrated into Windows Server 2008. Therefore, RTM milestone files apply only to Windows Vista. RTM milestone files have a 6.0.0000.xxxxxx version number.
• The MANIFEST files (.manifest) and MUM files (.mum) installed for each environment are listed separately. MUM and MANIFEST files, and the associated security catalog (.cat) files, are critical to maintaining the state of the updated component. The security catalog files (attributes not listed) are signed with a Microsoft digital signature.

For all supported x86-based versions of Windows Server 2008 and of Windows Vista

For all supported x64-based versions of Windows Server 2008 and of Windows Vista

For all supported IA-64-based versions of Windows Server 2008

Additional file information for Windows Server 2008 and Windows Vista

Additional files for all supported x86-based versions of Windows Server 2008 and of Windows Vista

Additional files for all supported x64-based versions of Windows Server 2008 and of Windows Vista

Additional files for all supported IA-64-based versions of Windows Server 2008

To work around this problem, run the Fc.exe command together with the /b (binary) switch.

Note Binary mode does not show the location of the differences.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Fc.exe is a command that compares two files or two sets of files, and then it displays the differences between them.