How can we lock the file with DOS?

To lock a file in DOS, you can use the ATTRIB command to set the file as read-only, which prevents modifications. The command syntax is ATTRIB +R filename, where "filename" is the name of the file you want to lock. Additionally, you can set file permissions using attributes like hidden or system. However, true file locking in DOS is limited, as it doesn't provide robust file locking mechanisms like modern operating systems.