Note: This API call is for DOS and Win16 personality only. Use Family API for portability.

INT 21H

AH	Description	Version
00H	Program terminate	1.0+
01H	Character input	1.0+
02H	Character output	1.0+
03H	Auxiliary input	1.0+
04H	Auxiliary output	1.0+
05H	Printer output	1.0+
06H	Direct console I/O	1.0+
07H	Direct console input without echo	1.0+
08H	Console input without echo	1.0+
09H	Display string	1.0+
0AH	Buffered keyboard input	1.0+
0BH	Get input status	1.0+
0CH	Flush input buffer and input	1.0+
0DH	Disk reset	1.0+
0EH	Set default drive	1.0+
0FH	Open file	1.0+
10H	Close file	1.0+
11H	Find first file	1.0+
12H	Find next file	1.0+
13H	Delete file	1.0+
14H	Sequential read	1.0+
15H	Sequential write	1.0+
16H	Create or truncate file	1.0+
17H	Rename file	1.0+
18H	Reserved	1.0+
19H	Get default drive	1.0+
1AH	Set disk transfer address	1.0+
1BH	Get allocation info for default drive	1.0+
1CH	Get allocation info for specified drive	1.0+
1DH	Reserved	1.0+
1EH	Reserved	1.0+
1FH	Get disk parameter block for default drive	1.0+
20H	Reserved	1.0+
21H	Random read	1.0+
22H	Random write	1.0+
23H	Get file size in records	1.0+
24H	Set random record number	1.0+
25H	Set interrupt vector	1.0+
26H	Create PSP	1.0+
27H	Random block read	1.0+
28H	Random block write	1.0+
29H	Parse filename	1.0+
2AH	Get date	1.0+
2BH	Set date	1.0+
2CH	Get time	1.0+
2DH	Set time	1.0+
2EH	Set verify flag	1.0+
2FH	Get disk transfer address	2.0+
30H	Get DOS version	2.0+
31H	Terminate and stay resident	2.0+
32H	Get disk parameter block for specified drive	2.0+
33H	Get or set Ctrl-Break	2.0+
34H	Get InDOS flag pointer	2.0+
35H	Get interrupt vector	2.0+
36H	Get free disk space	2.0+
37H	Get or set switch character	2.0+
38H	Get or set country info	2.0+
39H	Create subdirectory	2.0+
3AH	Remove subdirectory	2.0+
3BH	Change current directory	2.0+
3CH	Create or truncate file	2.0+
3DH	Open file	2.0+
3EH	Close file	2.0+
3FH	Read file or device	2.0+
40H	Write file or device	2.0+
41H	Delete file	2.0+
42H	Move file pointer	2.0+
43H	Get or set file attributes	2.0+
44H	I/O control for devices	2.0+
45H	Duplicate handle	2.0+
46H	Redirect handle	2.0+
47H	Get current directory	2.0+
48H	Allocate memory	2.0+
49H	Release memory	2.0+
4AH	Reallocate memory	2.0+
4BH	Execute program	2.0+
4CH	Terminate with return code	2.0+
4DH	Get program return code	2.0+
4EH	Find first file	2.0+
4FH	Find next file	2.0+
50H	Set current PSP	2.0+
51H	Get current PSP	2.0+
52H	Get DOS internal pointers (SYSVARS)	2.0+
53H	Create disk parameter block	2.0+
54H	Get verify flag	2.0+
55H	Create program PSP	2.0+
56H	Rename file	2.0+
57H	Get or set file date and time	2.0+
58H	Get or set allocation strategy	2.11+
59H	Get extended error info	3.0+
5AH	Create unique file	3.0+
5BH	Create new file	3.0+
5CH	Lock or unlock file	3.0+
5DH	File sharing functions	3.0+
5EH	Network functions	3.0+
5FH	Network redirection functions	3.0+
60H	Qualify filename	3.0+
61H	Reserved	3.0+
62H	Get current PSP	3.0+
63H	Get DBCS lead byte table pointer	3.0+
64H	Set wait for external event flag	3.2+
65H	Get extended country info	3.3+
66H	Get or set code page	3.3+
67H	Set handle count	3.3+
68H	Commit file	3.3+
69H	Get or set media id	4.0+
6AH	Commit file	4.0+
6BH	Reserved	4.0+
6CH	Extended open/create file	4.0+