Contributor: SELOM OFORI
{please use only on floppy.
It reads sector 0 which is the boot sector for a floppy and
the partition table for a hard disk.
It never writes to disk anyways....
}
program readboot;
uses dos, crt;
type
boot_structure = record
jmp_instruction : array[1..3] of byte;
oem_name : array[1..8] of char;
bytes_per_sector : word;
sectors_per_cluster : byte;
reserved_sectors : word;
fat_copies : byte;
root_entries : word;
total_sectors : word;
media_descriptor : byte;
sectors_per_fat : word;
sectors_per_track : word;
number_of_heads : word;
hidden_sectors : word;
total_sector_fixed : array[1..2] of word;
drive_number : byte;
reserved : byte;
ext_boot_sig : byte;
serial_number : array[1..2] of word;
volume_name : array[1..11] of char;
file_system_id : array[1..8] of char;
boot_program_code : array[1..450] of char;
signature_bytes : array[1..2] of byte;
end;
var
bootbuf : boot_structure;
ch : char;
arg : string;
drive : byte;
result : word;
{ for this procedure.. its in ASM ( doesn't make it any faster.. :) )
VAR BUF can either be an array, pointer or record
DRIVE is the drive number ( A=0, B=1 etc )
NUMBER is the number of sectors to read
LOGICAL is the sector to which to start reading
}
procedure absread( var buf; drive : byte;
number, logical : word ); assembler;
asm
push bp
push ds
xor ax,ax
mov result,ax
mov al,drive
mov cx,number
mov dx,logical
lds bx,buf
int 25h { you can change to 26h to write to disk }
pop bx
pop ds
pop bp
jnb @1
mov result,ax
@1:
end;
procedure commandline_help;
begin
writeln('Usage: Readboot < drive > ');
halt;
end;
procedure commandline;
var regs : registers;
begin
case paramcount of
1 : begin
arg := paramstr( 1 );
ch := arg[ 1 ];
ch := upcase( ch );
if ch in [ #65..#90 ] then drive := ord( ch ) - 65;
regs.AH := $36;
regs.DL := drive + 1;
msdos( regs );
if regs.AX = $FFFF then
begin
writeln('Drive ', ch, ':\ does not exist!');
halt;
end;
end;
else commandline_help;
end;
end;
procedure display_boot;
begin
with bootbuf do
begin
write('OEM Name......... : ':30 );
highvideo; writeln( oem_name ); normvideo;
write('Bytes Per Sector. : ':30 );
highvideo; writeln( bytes_per_sector ); normvideo;
{ etc, etc.... }
end;
end;
begin
commandline;
absread( bootbuf, drive, 1, 0 );
display_boot;
end.
Here's the structure of the boot sector
{ DOS Volume Boot Sector Format [DVB]
Offset Size Description
00h 3 BYTEs jump instruction to boot program code
03h 8 BYTEs OEM name and DOS version ("IBM 4.0")
0Bh 1 WORD bytes per sector( usually 512 )
0Dh 1 BYTE sectors per cluster( must be power of 2 )
0Eh 1 WORD reserved sectors( boot sectors - usually 1 )
10h 1 BYTE FAT copies ( usually 2 )
11h 1 WORD maximum root diretory entries ( usually 512 )
13h 1 WORD total sectors( if partition <= 32M, else 0 )
15h 1 BYTE media descriptor byte ( F8h for hard disks )
16h 1 WORD sectors per FAT
18h 1 WORD sectors per track
1Ah 1 WORD number of heads
1Ch 1 DWORD hidden sectors(if partition <= 32M,
1 word only)
The following information is for DOS 4.0 and later version else 00h:
20h 1 DWORD total sectos( if partition > 32M, else 0 )
24h 1 BYTE physical drive number (00h=floppy, 80h=fixed)
25h 1 BYTE reserved( 00h )
26h 1 BYTE extended boot record signature( 29h )
27h 1 DWORD volume serial number
2Bh 11 BYTEs volume label("NO NAME " stored if no label)
36h 8 BYTEs file system ID ("FAT12 " or "FAT16 ")
The following information applies to all DOS versions:
3Eh 450 BYTEs Boot program code
1FEh 2 BYTEs signature bytes ( 55AAh )
}
please use only on floppy.
It reads sector 0 which is the boot sector for a floppy and
the partition table for a hard disk.
It never writes to disk anyways....
It will read the boot sector from a floppy and display it.
___------------------< Cut here >-----------------------------------------
program readboot;
uses dos, crt;
type
boot_structure = record
jmp_instruction : array[1..3] of byte;
oem_name : array[1..8] of char;
bytes_per_sector : word;
sectors_per_cluster : byte;
reserved_sectors : word;
fat_copies : byte;
root_entries : word;
total_sectors : word;
media_descriptor : byte;
sectors_per_fat : word;
sectors_per_track : word;
number_of_heads : word;
hidden_sectors : word;
total_sector_fixed : array[1..2] of word;
drive_number : byte;
reserved : byte;
ext_boot_sig : byte;
serial_number : array[1..2] of word;
volume_name : array[1..11] of char;
file_system_id : array[1..8] of char;
boot_program_code : array[1..450] of char;
signature_bytes : array[1..2] of byte;
end;
var
bootbuf : boot_structure;
ch : char;
arg : string;
drive : byte;
result : word;
{ for this procedure.. its in ASM ( doesn't make it any faster.. :) )
VAR BUF can either be an array, pointer or record
DRIVE is the drive number ( A=0, B=1 etc )
NUMBER is the number of sectors to read
LOGICAL is the sector to which to start reading
}
procedure absread( var buf; drive : byte;
number, logical : word ); assembler;
asm
push bp
push ds
xor ax,ax
mov result,ax
mov al,drive
mov cx,number
mov dx,logical
lds bx,buf
int 25h { you can change to 26h to write to disk }
pop bx
pop ds
pop bp
jnb @1
mov result,ax
@1:
end;
procedure commandline_help;
begin
writeln('Usage: Readboot < drive > ');
halt;
end;
procedure commandline;
var regs : registers;
begin
case paramcount of
1 : begin
arg := paramstr( 1 );
ch := arg[ 1 ];
ch := upcase( ch );
if ch in [ #65..#90 ] then drive := ord( ch ) - 65;
regs.AH := $36;
regs.DL := drive + 1;
msdos( regs );
if regs.AX = $FFFF then
begin
writeln('Drive ', ch, ':\ does not exist!');
halt;
end;
end;
else commandline_help;
end;
end;
procedure display_boot;
begin
with bootbuf do
begin
write('OEM Name......... : ':30 );
highvideo; writeln( oem_name ); normvideo;
write('Bytes Per Sector. : ':30 );
highvideo; writeln( bytes_per_sector ); normvideo;
{ etc, etc.... }
end;
end;
begin
commandline;
absread( bootbuf, drive, 1, 0 );
display_boot;
end.