When an application starts, it inherits the current directory and drive from the application that starts it. An application can determine which directory and drive are current by using DosQueryCurrentDir and DosQueryCurrentDisk. An application can change the current directory and drive of the file system by using DosSetCurrentDir and DosSetDefaultDisk.

When an application creates a new file, the system adds a file entry to the specified directory. Each directory can have any number of entries, up to the physical limit of the disk. An application can create new directories and delete existing directories by using DosCreateDir and DosDeleteDir. Before a directory can be deleted, it must be empty; if there are files or directories in that directory, they must be deleted or moved. An application can delete a file by using DosDelete or move a file to another directory by using DosMove.