0	Program terminate.
1	Keyboard input.
2	Display output.
3	Aux input.
4	Aux output.
5	Printer output.
6	Direct I/O.
7	Direct I/O no echo.
8	Console input no echo.
9	Print string.
A	Buffered keyboard input.
B	Check standard input status.
C	Clear standard input buffer and invoke a standard input function.
D	Disk reset.
E	Select disk.
F	Open file.
10	Close file.
11	Search for the first entry.
12	Search for next.
13	Delete file.
14	Sequential read.
15	Sequential write.
16	Create file.
17	Rename file.
18
19	Current disk.
1A	Set disk transfer address.
1B	Allocation table information.
1C	Allocation table information for specific drive.
1D
1E
1F
20
21	Random read.
22	Random write.
23	File size.
24	Set random record field.
25	Set interrupt vector.
26	Create a new program segment.
27	Random block read.
28	Random block write.
29	Parse filename.
2A	Get date.
2B	Set date.
2C	Get time.
2D	Set time.
2E	Set/reset verify switch.
2F	Get DTA.
30	Get Dos version number.
31	Terminates process and remain resident.
32
33	Ctrl Break check.
34
35	Get vector.
36	Get disk free space.
37
38	Return country dependent information.
39	Creat a sub-directory (mkdir).
3A	Remove a directory entry (rmdir).
3B	Change the current directory (chdir).
3C	Create a file. (creat)
3D	Open a file.
3E	Close a file handle.
3F	Read from a file or device.
40	Write to a file or device.
41	Delete a file fro a specified directory (unlink).
42	Move file read/write pointer (lseek).
43	Change file mode (chmod).
44	I/O control for devices (ioctl).
45	Duplicate a file handle (dup).
46	Force a duplicate of a handle.
47	Get Current directory.
48	Allocate memory.
49	Free allocated memory.
4A	Setblock-Modify allocate memory blocks.
4B	Load or execute a program (exec).
4C	Terminate a process (exit).
4D	Retrieve the return code of a sub-process (wait).
4E	Find first matching file (find first)
4F	Find next matching file.
50
51
52
53
54	Get verify state.
55
56	Rename a file.
57	Get/Set a file's date and time.