数组及指针问题(100分)

//定义全局变量数组 writebuf
var
writebuf: array[0..127] of char;

//函数decode将参数数组全部设为a
function decode(data:array[0..127] of char)
begin
for i:=0 to 127 do data:='a';
end;

//调用函数
decode(writebuf)
问题在于 调用此函数后，writebuf数组的值没有改变，
请问如何传递一个数组到一个函数，并且在此函数中改变传递过来数组的值，好象可以用指针，具体怎么来实现，麻烦各位大侠给改一下。

传递数组的地址啊,使用指针来控制下移,你这样写函数肯定不对撒!

能给写一下代码吗，实在是头晕啊，感谢！

unit Unit2;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
writebuf: array[0..10] of char;

implementation

{$R *.dfm}
function decode(datachar)char;
var
i:integer;
begin
try
for i:=0 to 9 do
begin
data := 'a';
end;
result := data;
except
result := nil;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
i:integer;
begin
writebuf := '0123456789';
for i:=0 to length(decode(writebuf))-1 do
begin
memo1.Lines.Add(writebuf);
end;

end;

end.

这样修改一下更好:
unit Unit2;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls;

type
TForm1 = class(TForm)
Button1: TButton;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
Form1: TForm1;
writebuf: array[0..10] of char;

implementation

{$R *.dfm}
function decode(datachar)char;
var
i:integer;
begin
try
for i:=0 to length(data)-1 do
begin
data := 'a';
end;
result := data;
except
result := nil;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
i:integer;
begin
writebuf := '0123456789';
memo1.Lines.Clear;
memo1.Lines.Add(writebuf);
for i:=0 to length(decode(writebuf))-1 do
begin
memo1.Lines.Add(writebuf);
end;

end;

end.

请问 cqwty 我这样做怎么报以下错误
[Error] Unit1.pas(297): Incompatible types: 'Byte' and 'PAnsiChar'

ok了，谢谢