在delphi中函数怎么用？(100分)

在delphi中函数怎么用？一般加在什么位置？
声明后在什么位置用如何方法调用？
例如以下这个读硬盘序号的函数，如何调用？

function GetIdeDiskSerialNumber : String;
type
TSrbIoControl = packed record
HeaderLength : ULONG;
Signature : Array[0..7] of Char;
Timeout : ULONG;
ControlCode : ULONG;
ReturnCode : ULONG;
Length : ULONG;
end;
SRB_IO_CONTROL = TSrbIoControl;
PSrbIoControl = ^TSrbIoControl;

TIDERegs = packed record
bFeaturesReg : Byte; // Used for specifying SMART "commands".
bSectorCountReg : Byte; // IDE sector count register
bSectorNumberReg : Byte; // IDE sector number register
bCylLowReg : Byte; // IDE low order cylinder value
bCylHighReg : Byte; // IDE high order cylinder value
bDriveHeadReg : Byte; // IDE drive/head register
bCommandReg : Byte; // Actual IDE command.
bReserved : Byte; // reserved. Must be zero.
end;
IDEREGS = TIDERegs;
PIDERegs = ^TIDERegs;

TSendCmdInParams = packed record
cBufferSize : DWORD;
irDriveRegs : TIDERegs;
bDriveNumber : Byte;
bReserved : Array[0..2] of Byte;
dwReserved : Array[0..3] of DWORD;
bBuffer : Array[0..0] of Byte;
end;
SENDCMDINPARAMS = TSendCmdInParams;
PSendCmdInParams = ^TSendCmdInParams;

TIdSector = packed record
wGenConfig : Word;
wNumCyls : Word;
wReserved : Word;
wNumHeads : Word;
wBytesPerTrack : Word;
wBytesPerSector : Word;
wSectorsPerTrack : Word;
wVendorUnique : Array[0..2] of Word;
sSerialNumber : Array[0..19] of Char;
wBufferType : Word;
wBufferSize : Word;
wECCSize : Word;
sFirmwareRev : Array[0..7] of Char;
sModelNumber : Array[0..39] of Char;
wMoreVendorUnique : Word;
wDoubleWordIO : Word;
wCapabilities : Word;
wReserved1 : Word;
wPIOTiming : Word;
wDMATiming : Word;
wBS : Word;
wNumCurrentCyls : Word;
wNumCurrentHeads : Word;
wNumCurrentSectorsPerTrack : Word;
ulCurrentSectorCapacity : ULONG;
wMultSectorStuff : Word;
ulTotalAddressableSectors : ULONG;
wSingleWordDMA : Word;
wMultiWordDMA : Word;
bReserved : Array[0..127] of Byte;
end;
PIdSector = ^TIdSector;

const
IDE_ID_FUNCTION = $EC;
IDENTIFY_BUFFER_SIZE = 512;
DFP_RECEIVE_DRIVE_DATA = $0007c088;
IOCTL_SCSI_MINIPORT = $0004d008;
IOCTL_SCSI_MINIPORT_IDENTIFY = $001b0501;
DataSize = sizeof(TSendCmdInParams)-1+IDENTIFY_BUFFER_SIZE;
BufferSize = SizeOf(SRB_IO_CONTROL)+DataSize;
W9xBufferSize = IDENTIFY_BUFFER_SIZE+16;
var
hDevice : THandle;
cbBytesReturned : DWORD;
pInData : PSendCmdInParams;
pOutData : Pointer; // PSendCmdOutParams
Buffer : Array[0..BufferSize-1] of Byte;
srbControl : TSrbIoControl absolute Buffer;

procedure ChangeByteOrder( var Data; Size : Integer );
var ptr : PChar;
i : Integer;
c : Char;
begin
ptr := @Data;
for i := 0 to (Size shr 1)-1 do
begin
c := ptr^;
ptr^ := (ptr+1)^;
(ptr+1)^ := c;
Inc(ptr,2);
end;
end;

begin
Result := '';
FillChar(Buffer,BufferSize,#0);
if Win32Platform=VER_PLATFORM_WIN32_NT then
begin // Windows NT, Windows 2000
// Get SCSI port handle
hDevice := CreateFile( '//./Scsi0:',
GENERIC_READ or GENERIC_WRITE,
FILE_SHARE_READ or FILE_SHARE_WRITE,
nil, OPEN_EXISTING, 0, 0 );
if hDevice=INVALID_HANDLE_VALUE then Exit;
try
srbControl.HeaderLength := SizeOf(SRB_IO_CONTROL);
System.Move('SCSIDISK',srbControl.Signature,8);
srbControl.Timeout := 2;
srbControl.Length := DataSize;
srbControl.ControlCode := IOCTL_SCSI_MINIPORT_IDENTIFY;
pInData := PSendCmdInParams(PChar(@Buffer)
+SizeOf(SRB_IO_CONTROL));
pOutData := pInData;
with pInData^ do
begin
cBufferSize := IDENTIFY_BUFFER_SIZE;
bDriveNumber := 0;
with irDriveRegs do
begin
bFeaturesReg := 0;
bSectorCountReg := 1;
bSectorNumberReg := 1;
bCylLowReg := 0;
bCylHighReg := 0;
bDriveHeadReg := $A0;
bCommandReg := IDE_ID_FUNCTION;
end;
end;
if not DeviceIoControl( hDevice, IOCTL_SCSI_MINIPORT,
@Buffer, BufferSize, @Buffer, BufferSize,
cbBytesReturned, nil ) then Exit;
finally
CloseHandle(hDevice);
end;
end
else
begin // Windows 95 OSR2, Windows 98
hDevice := CreateFile( '//./SMARTVSD', 0, 0, nil,
CREATE_NEW, 0, 0 );
if hDevice=INVALID_HANDLE_VALUE then Exit;
try
pInData := PSendCmdInParams(@Buffer);
pOutData := @pInData^.bBuffer;
with pInData^ do
begin
cBufferSize := IDENTIFY_BUFFER_SIZE;
bDriveNumber := 0;
with irDriveRegs do
begin
bFeaturesReg := 0;
bSectorCountReg := 1;
bSectorNumberReg := 1;
bCylLowReg := 0;
bCylHighReg := 0;
bDriveHeadReg := $A0;
bCommandReg := IDE_ID_FUNCTION;
end;
end;
if not DeviceIoControl( hDevice, DFP_RECEIVE_DRIVE_DATA,
pInData, SizeOf(TSendCmdInParams)-1, pOutData,
W9xBufferSize, cbBytesReturned, nil ) then Exit;
finally
CloseHandle(hDevice);
end;
end;
with PIdSector(PChar(pOutData)+16)^ do
begin
ChangeByteOrder(sSerialNumber,SizeOf(sSerialNumber));
SetString(Result,sSerialNumber,SizeOf(sSerialNumber));
end;
end;

在delphi中函数怎么用？一般加在什么位置？
函数一般有返回值,放在=号右边(例:下面),也可以直接调用(例
ShowWindow(handle,SW_HIDE);

声明后在什么位置用如何方法调用？
可以不声明(不引出),在实现后调用
声明后其它单元引用后就可以调用
在
http://www.delphibbs.com/delphibbs/dispq.asp?lid=1425701
中有好多函数声明及调用例子

例如以下这个读硬盘序号的函数，如何调用？
var
s:string;
begin
s:=GetIdeDiskSerialNumber ;
showmessage(s);
end;

to ysai :编译通不过，不知是不是这个函数的问题

是函数问题
看哪行有错(message view中双击有错的行),再改正
我对上面的函数没有研究,不懂,就不乱说了

这么晚了，多谢你了，先把分给你