使用如下API函數
BOOL GetDiskFreeSpace(
LPCTSTR lpRootPathName, // address of root path
LPDWORD lpSectorsPerCluster, // address of sectors per cluster
LPDWORD lpBytesPerSector, // address of bytes per sector
LPDWORD lpNumberOfFreeClusters, // address of number of free clusters
LPDWORD lpTotalNumberOfClusters // address of total number of clusters
);
Parameters
lpRootPathName
Points to a null-terminated string that specifies the root directory of the disk to return information about. If lpRootPathName
is NULL, the function uses the root of the current directory.
lpSectorsPerCluster
Points to a variable for the number of sectors per cluster.
lpBytesPerSector
Points to a variable for the number of bytes per sector.
lpNumberOfFreeClusters
Points to a variable for the total number of free clusters on the disk.
lpTotalNumberOfClusters
Points to a variable for the total number of clusters on the disk.
Return Values
If the function succeeds, the return value is nonzero.
If the function fails, the return value is zero. To get extended error information, call GetLastError.
例子：
procedure TForm1.Button1Click(Sender: TObject);
var DriveString:String;
sec1, byt1, cl1, cl2: LongWord;
Disk_FreeSpace : real;
begin
GetDiskFreeSpace('d:\', sec1, byt1, cl1, cl2);
Disk_FreeSpace := (cl1 / (1024*1024*1024))*sec1*byt1;
showmessage(format('該驅動器容量是%0.3fG',[Disk_FreeSpace]));
end;
上面的程序是將數據從字節單位轉換爲G的，之所以這樣做，是爲了避免當磁盤容量大于DELPHI基本數據類型所能存儲的最大值，避免溢出。如果想獲得以字節爲單位的，那麽將遇到大數相乘的問題。
下面提供一個大數相乘的算法，他接收兩個字符串，輸出這個兩個字符串的乘積（當然字符串裏都是數字）
function TForm1.XAddY(x, y: string): string;
var
a,b,c:array[1..1000] of integer;
i,j,k,l,m,code:integer;
s,p,r:string;
begin
s := x; //兩個要相乘的字符串
p := y;
l:=length(s);
for i:=l downto 1 do
Val(s[i],a[l-i+1],code);
m:=length(p);
for i:=m downto 1 do
Val(p[i],b[m-i+1],code);
for j:=1 to m do
for i:=1 to l do
begin
if c[i+j-1]+a[i]*b[j]<=9 then begin
c[j+i-1]:=c[i+j-1]+a[i]*b[j];
k:=i+j-1;
end else begin
c[j+i-1]:=c[i+j-1]+(a[i]*b[j]) mod 10;
c[j+i]:=c[j+i]+ c[j+i-1] div 10+ (a[i]*b[j]) div 10;
c[i+j-1]:=c[i+j-1] mod 10;
k:=i+j;
end;
end;
r := '';
for i:=k downto 1 do
r := r+IntToStr(c[i]);
Result := r;
end;
下面我們就可以通過使用大數相乘的算法的得到磁盤的容量（用字節表示）
procedure TForm1.Button2Click(Sender: TObject);
var
sec1, byt1, cl1, cl2: LongWord;
Disk_FreeSpace : string;
begin
GetDiskFreeSpace('d:\', sec1, byt1, cl1, cl2);
Disk_FreeSpace := XAddY(inttostr(cl1),inttostr(sec1*byt1));
showmessage(format('該驅動器容量是%s字節',[Disk_FreeSpace]));
end;
程序完整的代碼如下：
unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;
type
TForm1 = class(TForm)
Button1: TButton;
Label1: TLabel;
Label2: TLabel;
Button2: TButton;
Label3: TLabel;
procedure Button1Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
private
{ Private declarations }
public
function XAddY(x : string;y:string) : string;
end;
var
Form1: TForm1;
implementation
{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var DriveString:String;
sec1, byt1, cl1, cl2: LongWord;
Disk_FreeSpace : real;
begin
GetDiskFreeSpace('d:\', sec1, byt1, cl1, cl2);
Disk_FreeSpace := (cl1 / (1024*1024*1024))*sec1*byt1;
showmessage(format('該驅動器容量是%0.3fG',[Disk_FreeSpace]));
end;
function TForm1.XAddY(x, y: string): string;
var
a,b,c:array[1..1000] of integer;
i,j,k,l,m,code:integer;
s,p,r:string;
begin
s := x; //兩個要相乘的字符串
p := y;
l:=length(s);
for i:=l downto 1 do
Val(s[i],a[l-i+1],code);
m:=length(p);
for i:=m downto 1 do
Val(p[i],b[m-i+1],code);
for j:=1 to m do
for i:=1 to l do
begin
if c[i+j-1]+a[i]*b[j]<=9 then begin
c[j+i-1]:=c[i+j-1]+a[i]*b[j];
k:=i+j-1;
end else begin
c[j+i-1]:=c[i+j-1]+(a[i]*b[j]) mod 10;
c[j+i]:=c[j+i]+ c[j+i-1] div 10+ (a[i]*b[j]) div 10;
c[i+j-1]:=c[i+j-1] mod 10;
k:=i+j;
end;
end;
r := '';
for i:=k downto 1 do
r := r+IntToStr(c[i]);
Result := r;
end;
procedure TForm1.Button2Click(Sender: TObject);
var
sec1, byt1, cl1, cl2: LongWord;
Disk_FreeSpace : string;
begin
GetDiskFreeSpace('d:\', sec1, byt1, cl1, cl2);
Disk_FreeSpace := XAddY(inttostr(cl1),inttostr(sec1*byt1));
showmessage(format('該驅動器容量是%s字節',[Disk_FreeSpace]));
end;
end.