For each file on disk, there is an inode for that file (also stored on the disk) is a struct containing file information including

• creation, last modification times
• file owner
• file type (ordinary file, directory, named pipe)
• file access permissions
• location of data blocks on disk

When a file is opened its inode is read into an available slot in the inode table in memory. The in memory inode table contains a few more members including

• reference count - how many different file opens reference this file.
• device (disk) where the inode is located.

Even if more than one process has a file open, there will only be one entry in the inode table for that file, but the reference count will reflect the number of uses of that inode.