2.3 Directory Entry Structure
The directory structure of the file system consists of a linked list of linked lists. Each directory entry contains a pointer to the next sibling (SiblingPtr) at its level in the hierarchy, and also a pointer (PrimaryPtr) to its children which may be other directories (DirEntrys) or files (FileEntrys). Note that a DirEntry can be superseded by including a valid pointer (SecondaryPtr) to the replacement DirEntry. In this case, the PrimaryPtr and SiblingPtr are invalid.
The first, or root, Directory Entry must have a name of "ROOT ".
struct DirEntry
{
word Status
dword SiblingPtr
dword PrimaryPtr
dword SecondaryPtr
byte Attributes
word Time
word Date
word VarStructLen
byte NameLen
byte Name[8]
byte Ext[3]
}