INT 21,3D - Open File Using Handle

AH = 3D

AL = open access mode

00 read only

01 write only

02 read/write

DS:DX = pointer to an ASCIIZ file name

on return:

AX = file handle if CF not set

= error code if CF set (see ~DOS ERROR CODES~)

% Access modes in AL:

¦7¦6¦5¦4¦3¦2¦1¦0¦ AL

¦ ¦ ¦ ¦ ¦ +-------- read/write/update access mode

¦ ¦ ¦ ¦ +--------- reserved, always 0

¦ +-------------- sharing mode (see below) (DOS 3.1+)

+--------------- 1 = private, 0 = inheritable (DOS 3.1+)

% Sharing mode bits (DOS 3.1+): Access mode bits:

% 654 210

000 compatibility mode (exclusive) 000 read access

001 deny others read/write access 001 write access

010 deny others write access 010 read/write access

011 deny others read access

100 full access permitted to all

- will open normal, hidden and system files

- file pointer is placed at beginning of file