Category: DOS kernel
INT 21 - DOS 3.4/4.0 - GET CURRENT CPSW STATE
AX = 3303h
Return: DL = current CPSW
Notes: this function and AX=3304h were intended to support a proposed
code-page switching flag (using the WORD at offset 0Ch in the DOS
directory entry for codepage information); however, this function
has always been a NOP in public releases of DOS and OS/2.
See _DOS_Internals_ Chapter 2 for more information.
the released MS-DOS 4.00 IO.SYS has an undocumented CONFIG.SYS
directive named CPSW= and that beside others the MS-DOS 4.00 ATTRIB
supported a number of undocumented special parameters for
"predefined" Extended Attributes (EAs) e.g.
ATTRIB filename [(CODEPAGE|CP)[=new_value]].
this function does not use any of the DOS-internal stacks and may
thus be called at any time. It is directly dispatched from
the INT 21h entry point with interrupts disabled.