These functions are called by DOS (v3.0+) internally. Most of them require that an internal DOS stack is in use, and somtimes that DS is set to the DOS data segment (in which case, under MS-compatible DOSes, SS will equal DS). They are accessed through the Interrupt 2Fh interface, with AH set to 12h.
On exit: AL = 0FFh
This call is provided for compatibility with the multiplex interrupt specification.
On entry: SS = DOS DS, SDA current SFT entry pointer -> file to close
On exit: (CF set on error) BX destroyed, CX new ref. count for SFT entry, ES:DI -> SFT entry
On entry: ES:DI -> null terminated string
On exit: CX = length of string including null character