INT 21,13 - Delete File Using FCB

AH = 13h

DS:DX = pointer to an unopened ~FCB~

on return:

AL = 00 if file deleted

= FF if file not found

- deletes unopened file with normal attributes

- FCB must contain drive id, filename, and extension before call

- "?" wildcard supported after DOS 2.1, "*" supported by DOS 3.x+

- DOS 2.x allowed deletion of a subdirectory if ~XFCB~ was provided,

even if files existed, causing lost clusters. DOS 3.x does not