Find first ASCIIZ (INT 21h, 4Eh - FIND FIRST)

        Searches disk for a matching file. The filename and the find-next
        information is placed in the current DTA

        Entry:
          AH = 4Eh
          CX = search attributes
          DS:DX = pointer to ASCIIZ filename
        Return:
          CF = 1 if error
          AX = Error Code if any

        [DTA] = data block
                    byte  00h:     drive letter (undocumented)
                    bytes 01h-0Bh: search template (undocumented)
                    bytes 0Ch-14h: reserved
                    byte  15h:     attribute of file found
                    bytes 16h-17h: file time
                    bytes 18h-19h: file date
                    bytes 1Ah-1Dh: file size
                    bytes 1Eh-3Ah: ASCIZ filename+extension