Nonzero indicates success. Zero indicates failure. To get extended error information, call GetLastError.

For All Platforms:

This function closes handles to the following objects:

• Communications device
  
• Database
  
• Database enumeration context
  
• Event
  
• File
  
• File-mapping object
  
• Mutex
  
• Process
  
• Socket
  
• Thread
  

This function invalidates the specified object handle, decrements the object's handle count, and performs object retention checks. After the last handle to an object is closed, the object is removed from the system. Persistent objects, such as databases and files, remain in storage, but must be re-opened to be accessed again.

Closing a thread handle does not terminate the associated thread. To remove a thread object, you must terminate the thread, and then close all handles to the thread.

Use this function to close handles returned by calls to the CreateFile function. Use the FindClose function to close handles returned by calls to the FindFirstFile function.

When an application running in user mode calls this function, the kernel calls internal functions that clean up any associated resources, such as MyFileSystem_PreCloseHandle and MyFileSystem_CloseHandle.

For Windows Embedded CE:

In the past, when a user-mode call closed a handle, a failure of the internal preclose and close functions would cause this function to fail. This behavior has changed. With Windows Embedded CE 6.0 and later, this function succeeds on any valid handle, regardless of results that might be returned by the internal preclose and close functions.

Reference