INT 21,52 - Get Pointer to DOS "INVARS" (Undocumented)

AH = 52h

on return:

ES:BX = pointer to DOS "invars", a table of pointers used by DOS.

Known "invars" fields follow (varies with DOS version):

% Offset Size Description

-12 word sharing retry count (DOS 3.1-3.3)

-10 word sharing retry delay (DOS 3.1-3.3)

-8 dword pointer to current disk buffer (DOS 3.x)

-4 word pointer in DOS code segment of unread CON input;

0 indicates no unread input (DOS 3.x)

-2 word segment of first Memory Control Block (~MCB~)

00 dword pointer to first ~DRIVE PARAMETER TABLE~ (A:) in chain

04 dword pointer to DOS ~System File Table~ (SFT)

08 dword pointer to $CLOCK device driver

0C dword pointer to CON device driver

10 byte number of logical drives in system

11 word maximum bytes/block of any block device

13 dword pointer to DOS cache buffer header

17 18bytes NUL device header, first 4 bytes of device header

point to the next device in device chain