asked on

3.5 ' floppy disk serial number

in msdos window, typing dir (for drive with 3.5 disk)
shows Label, and serial number of the disk. How can I
read these numbers programatically, and is there a way of
changing the serial number programatically ?
how unique these numbers are ?

I need definite answer, please do not guess and lock the question.

ASKER CERTIFIED SOLUTION

tflai

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has

ASKER

well, the hint is close but I can not compile it.
there is no GlobalDosAlloc() or anything near, (GlobalAlloc cant do the job) and MK_FP as they think in dos.h not there? so if you can
get it work, let me know. I also think that this should not be
that involved, I thing I saw a function to read the disk volume serial no,
but I am not sure. Any way let me know if you can work it.

tflai

Here's some code from Microsoft's MSDN:

PSS ID Number: Q69223
Article last modified on 01-24-1995

5.10 6.00 6.00a 6.00ax 7.00 | 1.00 1.50

MS-DOS | WINDOWS

----------------------------------------------------------------------
The information in this article applies to:

- The C Run-time (CRT) included with:

- Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, and 6.0ax
- Microsoft C/C++ for MS-DOS, version 7.0
- Microsoft Visual C++ for Windows, versions 1.0 and 1.5
----------------------------------------------------------------------

SUMMARY
=======

Beginning with MS-DOS version 4.0, a semi-random 32-bit binary
identification number (ID) is assigned to each disk that MS-DOS
formats. The volume serial number (or ID) is stored at offset 27H to
2AH in the boot sector of each disk.

NOTE: code compiled with Visual C++ version 1.5 may yield the
following
message from Windows NT:

An applicaion has attempted to directly access the hard disk, which
cannot be supported. This may cause the application to function
incorrectly.

It provides Terminate and Ignore buttons. If the user is logged on
with
Administrative privileges, this will succeed for a FAT partition, else
it
fails for a FAT partition. It always fails for an NTFS partition.
After
clicking Terminate or Ignore the program returns with the error
message
that has been coded (error on int 25).

MORE INFORMATION
================

The following program illustrates how to retrieve this information:

/***************************************************************/
/* */
/* This program reads the volume serial number (or ID) from */
/* the boot sector of a specified disk. The DOS interrupt 25 */
/* Absolute Disk Read is used to read in the boot sector. */
/* */
/* Note: The volume ID is only implemented from MS-DOS 4.0 */
/* and later. */
/* */
/* The output consists of the OEM name and version of the */
/* disk-formatting program (stored at offset 03H to 0AH in the */
/* boot sector), the disk volume label, and the disk-volume */
/* serial number. */
/* */
/***************************************************************/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <dos.h>
#include <conio.h>

char bootsector[1024];
char volume[12];
char ver[9];
char block[10];

void main(void)
{
int ax, _far *p, drive;
struct find_t fileinfo;
char filename[13], _far *myvar, _far *q;
union REGS inregs, outregs;
struct SREGS segregs;

printf("Enter drive number (0=A,1=B,2=C, ...): ");
drive = getche() - '0';

/**************************************/
/* Parameter block for int 25H */
/* Bytes Description */
/* ------- ----------- */
/* 00H-03H 32-bit sector number */
/* 04H-05H Number of sectors to read */
/* 06H-07H Offset of buffer */
/* 08H-09H Segment of buffer */
/**************************************/

block[0] = block[1] = block[2] = block[3] = 0;
block[4] = 1;
block[5] = 0;

myvar = bootsector;

p = (int *)&block[6];
*p = FP_OFF(myvar);

p = (int *)&block[8];
*p = FP_SEG(myvar);

q = block;
inregs.h.al = (char)drive;
inregs.x.cx = -1;
inregs.x.bx = FP_OFF(q);
segregs.ds = FP_SEG(q);
ax = int86x(0x25, &inregs, &outregs, &segregs);

/*** Error routine ***/

if (outregs.x.cflag)
{
printf("\n\nerror on int 25\n");
printf("this is AX:%04X", ax);
exit(-1);
}

/*** Output ***/

printf("\n\nDrive %c\n-------\n\n", drive +'A');

strncpy(ver, &bootsector[3], 8);
printf("OEM name and version: %s\n", ver);

/* Use _dos_findfirst for the volume label */

filename[0] = (char)(drive + 'A');
filename[1] = '\0';
strcat(filename, ":\\*.*");
if(!_dos_findfirst(filename, _A_VOLID, &fileinfo))
printf("Volume name : %s\n", fileinfo.name);

/* Before printing serial number, check if version >= 4.x */

if ((ver[6] == '.') && (ver[5] >= '4') && (ver[5] <= '9'))
printf("Serial number : %02X%02X-%02X%02X\n\n",
(unsigned char) bootsector[0x2a],
(unsigned char) bootsector[0x29],
(unsigned char) bootsector[0x28],
(unsigned char) bootsector[0x27]);
}

Additional reference words: kbinf 5.10 6.00 6.00a 6.00ax 7.00 1.00
1.50
KBCategory: kbprg
KBSubcategory: CRTIss
=============================================================================
Copyright Microsoft Corporation 1995.

has

ASKER

Again I believe there is easier way now. I was able to find that reference,
and it says we can use GeVolumeInformation() API to get disk
volume information, if you can try this and see if you get the same
serial no of the disk, please let me know asap. thanks.

tflai

Yep! I did get the same serial number. (Except that the high and low WORD are reversed.)

has

ASKER

There is a SetVolumeLabel() API but I do not believe one can change
the serial no. it is given (randomly !) when the disk is formatted.
if not so please let me know. thanks