1 - DOS_GET_POSITION

Synopsys

Returns the current position in the file

Entry Parameters

Exit Parameters

If OK

Carry true

A corrupt

E HL = File pointer 0x000000…0xFFFFFF (16Mb)
E is most significant byte, L least

Otherwise:

Carry false

A = Error code

E HL = Corrupt

Always:

BC D IX corrupt, all other registers preserved.

2 - DOS_SET_POSITION

Synopsys

Sets the file pointer. This does not access the disk, nor does it check if the file pointer is >= 8 megabytes.

Entry Parameters

Exit Parameters

If OK

Carry true

A corrupt

Otherwise:

Carry false

A = Error code

Always:

BC DE HL IX corrupt, all other registers preserved.

3 - DOS_GET_EOF

Synopsys

Get the end of file (EOF) file position greater than all written byte positions. Does not affect the file pointer. Does not consider soft-EOF.

Entry Parameters

Exit Parameters

If OK

Carry true

A corrupt

E HL = File pointer 0x000000…0xFFFFFF (16Mb)
E is most significant byte, L least

Otherwise:

Carry false

A = Error code

E HL = Corrupt

Always:

BC D IX corrupt, all other registers preserved.

4 - DOS_GET_1346

Synopsys

Get the current location of the cache and RAMdisk.

Pages 1, 3, 4, 6 are considered as an array of 128 sector buffers (numbered 0...127), each of 512 bytes. The cache and RAMdisk occupy two separate (contiguous) areas of this array.

Any unused sector buffers may be used by the caller.

Note that the sizes may be smaller than those specified in DOS_SET_1346, as there is an (unpublished) maximum size of cache and a minimum size of RAMdisk (4 sectors).

Entry Parameters

None

Exit Parameters

D = First buffer of cache

E = Number of cache sector buffers

H = First buffer of RAM disk

L = Number of RAM disk sector buffers

Always:

AF BC IX corrupt, all other registers preserved.

5 - DOS_SET_1346

Synopsys

Rebuild the sector cache and RAM disk.

This routine is used to make some store available to the user, or to return store to DOS. Note that if the RAM disk is moved, or its size is changed, then all files thereon are erased.

Pages 1, 3, 4, 6 are considered as an array of 128 sector buffers (numbered 0...127), each of 512 bytes. The cache and RAMdisk occupy two separate (contiguous) areas of this array.

The location and size of the cache and RAMdisk can be specified separately; any remaining buffers are unused by DOS and are available to the caller.

Note that the sizes actually used may be smaller than those specified as in practice, there is a maximum cache size and a minimum size of RAMdisk (4 sectors).

A cache size of 0 will still work but will seriously impair the floppy disk performance.

This routine will fail if there are any files open on drive M:

Entry Parameters

Exit Parameters

If OK

Carry true

A corrupt

Otherwise:

Carry false

A = Error code

Always:

BC DE HL IX corrupt, all other registers preserved.

6 - DOS_FLUSH

Synopsys

Write any pending headers, data, directory entries for this drive.

This routine ensures that the disk is up-to-date. It can be called at any time, even when files are open.

Entry Parameters

Exit Parameters

If OK

Carry true

A corrupt

Otherwise:

Carry false

A = Error code

Always:

BC DE HL IX corrupt, all other registers preserved.

7 - DOS_SET_ACCESS

Synopsys

Try to change the access mode of an open file.

This routine will fail if the file is already open, in an incompatible access mode, or if write access is required for a read-only file or disk.

Entry Parameters

Exit Parameters

If OK

Carry true

A corrupt

Otherwise:

Carry false

A = Error code

Always:

BC DE HL IX corrupt, all other registers preserved.

8 - DOS_SET_ATTRIBUTES

Synopsys

Set a file's attributes.

Only the file attributes f1'...f4', t1'...t3' can be set or cleared. The interface attributes f5'...f8' are always 0.

This routine first sets the attributes specified in D, then clears those attributes specified in E, i.e. E has priority.

Entry Parameters

Exit Parameters

If OK

Carry true

A corrupt

Otherwise:

Carry false

A = Error code

Always:

BC DE HL IX corrupt, all other registers preserved.

9 - DOS_OPEN_DRIVE

Synopsys

Open the disk in this drive as a single file.

The whole disk is presented as a single file regardless of any real files on the disk. This routine can be used to examine/poke directories, files, etc. It should not be used by the uninitiated, the faint-hearted, or by anyone who values their files!

Sets file pointer to 0x000000 (0).

If there are any files open on this drive from other file numbers with shared-read access, then the disk can only be opened with shared-read access from this file number.

If there are any file open on this drive from other file numbers with exclusive access, then the disk cannot be opened from this file number.

Entry Parameters

Exit Parameters

If OK

Carry true

A corrupt

Otherwise:

Carry false

A = Error code

Always:

BC DE HL corrupt, all other registers preserved.

10 - DOS_SET_MESSAGE

Synopsys

Enable/disable disk error messages.

This should be used to make +3DOS aware of your own ALERT subroutine. When +3DOS detects an error, it will call your ALERT subroutine, passing to it the values documented below. The ALERT subroutine should print the text of the message that +3DOS passes it, then should wait for the user to press a key. If the key is in the reply string (that +3DOS also passes - version V1.0 only), then a 'ret' should be made with A = 0, 1 or 2, or containing the character (depending on the version of +3DOS).

Entry Parameters

Exit Parameters

HL = address of previous ALERT routine, 0 if none

Always:

AF BC DE IX corrupt, all other registers preserved.

ALERT implementations

Note that if you are substituting your own ALERT subroutine, the 'entry conditions' are the conditions passed to your subroutine and the 'exit conditions' are the values that your subroutine must produce and the registers you are allowed to corrupt.

There are two routine interfaces for ALERT, depending on which version of +3DOS is installed.

If you provide an ALERT function, you should have two subroutines, or one with switchable entry and exit conditions, and check the +3DOS version number before deciding which one to use.

+3DOS V1.0

Entry Parameters

Exit Parameters

A = Reply character

Always:

F BC DE HL IX corrupt, all other registers preserved.

+3DOS V1.1 and above

The second version allows the user to provide non-UK error messages and is generally more flexible, is present in +3DOS versions V1.1 and upwards.

Entry Parameters

Exit Parameters

A = Reply
0 = cancel
1 = retry
2 = ignore

Always:

F BC DE HL IX corrupt, all other registers preserved.

11 - DOS_REF_XDPB

Synopsys

Point at the XDPB for this drive. (The XDPB is required by the floppy disk driver routines.)

Entry Parameters

Exit Parameters

If OK:

Carry true

A corrupt

IX = Address of XDPB

Otherwise:

Carry false

A=Error code

IX corrupt

Always:

BC DE HL corrupt, all other registers preserved.

12 - DOS_MAP_B

Synopsys

Map drive B: to unit 0 or unit 1. This routine will fail if drive B: has files open.

If mapping B: to unit 0, then each time unit 0 is accessed, a check is made that the drive mapping is correct. If it isn't, then a reverse call to CHANGE DISK is made, to ask the user to change the disk in unit 0.

If mapping B: to unit 1, then if unit 1 does not exist, drive B: is disabled.

Entry Parameters

Exit Parameters

If OK:

Carry true

A corrupt

HL = Address of previous change disk routine, 0 if none

Otherwise:

Carry false

A corrupt

HL corrupt

Always:

BC DE IX corrupt, all other registers preserved.

Change Disk routine

If you are substituting your own CHANGE DISK subroutine, the 'entry conditions' are the conditions passed to your subroutine, and the 'exit conditions' are registers you are allowed to corrupt.

Entry Parameters

Exit Parameters

Always:

AF BC DE IX corrupt, all other registers preserved.