Windows stores temporary files with the extension .tmp. Temporary files store short-term information if the operating system or an application cannot allocate enough memory for all its tasks.
Applications and operating systems usually generate session-specific temporary files, meaning that the files are created and used only during the current use of an application or operating system. Windows deletes temporary files created by the operating system when it shuts down, as do most applications that employ temporary files.
Temporary files can always be opened using a notepad; however, depending on file type, temporary files may not be human-readable.
Right-click the .tmp file you want to open.
Select "Notepad" from the list of available programs.