This is the explanation of the ATTRIB command. It is EXTERNAL.

This command shows, changes or removes the read-only, archive, 
system, and hidden attributes in files.
Switches:
        +r/-r   sets/clears the read-only attribute
        +a/-a   sets/clears the archive attribute
        +s/-s   sets/clears the system attribute
        +h/-h   sets/clears the hidden attribute
         /s     processes files in current and all subdirectories

Example:
       attrib +r loan.dat
       This will make the file LOAN.DAT a read-only because the 
       read-only attribute was set.