main.pas

这是我给学生讲IEEE754浮点数机内表示时编的一个小程序

unit Main;

interface

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

type
  TForm1 = class(TForm)
    Button1: TButton;
    Edit1: TEdit;
    RichEdit1: TRichEdit;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    Memo1: TMemo;
    Label5: TLabel;
    Label6: TLabel;
    Label7: TLabel;
    RadioButton1: TRadioButton;
    RadioButton2: TRadioButton;
    Button2: TButton;
    Label8: TLabel;
    Edit2: TEdit;
    procedure Edit1Change(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure RadioButton1Click(Sender: TObject);
    procedure RadioButton2Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Memo1Change(Sender: TObject);
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}


// 10进制整数 转 2进制整数
function IntToBin(aInt: Int64): String;
var   
  vFlag: Boolean;
  vBit: Shortint;
begin   
  vFlag := aInt < 0;
  repeat
    vBit := aInt mod 2;
    aInt := aInt div 2;
    Result := IntToStr(Abs(vBit)) + Result;
  until aInt = 0;
  if vFlag then
    Result := '-' +  Result;
end;   

//2进制整数 转 10进制整数
Function BinToInt(Str :string) : Int64;
var
  vFlag: Boolean;
  aInt : Int64;
  i : integer;
begin
  if (Str[1] = '-') then
  begin
    vFlag := True;
    Str := Copy(Str, 2, Length(Str)-1);
  end
  else
    vFlag := False;
  aInt := 0;
  for i := 1 to Length(Str) do
    aInt := aInt * 2+ ORD(Str[i]) - 48;
  Result := aInt;
  if vFlag then
    Result := Result * (-1);
end;

//10进制纯小数 转 2进制小数
function DecimalToBin(aDec: Double): String;
var   
 vDoubleIt: Double;
begin   
  aDec := Frac(Abs(aDec));
  if aDec <> 0 then
  begin   
    vDoubleIt := aDec *  2;
    Result := IntToStr(Trunc(vDoubleIt)) + DecimalToBin(vDoubleIt);
  end;
end;

//2进制小数 转 10进制纯小数
function BinToDecimal(Str: String): Double;
var   
  i,j: Integer;
  aDec: Double;
begin
  j := Pos('.', Str);
  if (Str = '') then
  begin
    Result := 0;
    Exit;
  end;
  Str := copy(Str, j+1, Length(Str)-j -1);
  j := 0;
  aDec := 0;
  for i := 1 to Length(Str) do
  begin
    dec(j);
    aDec := aDec + (Ord(Str[i])-48)*Power(2,j);
  end;
  Result := aDec;
end;
    
//10进制有理数 转 2进制有理数
function FloatToBin(aFloat: Double): String;
var
  vInteger: Int64;
  vDecimal: Double;
begin   
  vInteger := Trunc(aFloat);
  vDecimal := Frac(aFloat);
  Result := IntToBin(vInteger) +  '.' + DecimalToBin(vDecimal);
end;

//2进制有理数 转 10进制有理数
function BinToFloat(Str: String): Double;
var
  vInteger: Int64;
  vDecimal: Double;
  j: Integer;
begin
  j := Pos('.', Str);
  if j <> 0 then
  begin
    vInteger := BinToInt(Copy(Str,1,j-1));
    vDecimal := BinToDecimal(Copy(Str,j+1,Length(Str)-j));
  end
  else
  begin
    vInteger := BinToInt(Str);
    vDecimal := 0;
  end;
  if vInteger > 0 then
    Result := vInteger +  vDecimal
  else
    Result := (Abs(vInteger) +  vDecimal) * (-1);
end;

procedure TForm1.Edit1Change(Sender: TObject);
begin
  Memo1.OnChange := nil;
  if (Edit1.Text <> '')then
    if (Pos('.',Edit1.Text) = 0) then
      Memo1.Text := IntToBin(StrToInt(Edit1.Text))
    else
      Memo1.Text := FloatToBin(StrToFloat(Edit1.Text));
  Memo1.OnChange := Memo1Change;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  x: Single;
  p: PDWORD;
  s: String;
  i: Integer;
  Y: Integer;
begin
  x := StrToFloat(Edit1.Text);
  p := @x;
  s := IntToBin(p^);
  Edit2.Text := IntToHex(p^,8);
  while Length(s) < 32 do
    s := '0' + s;
  s := copy(s,1,1) + ' ' + copy(s,2,8) + ' ' + copy(s,10,23);
  RichEdit1.Text := s;
  RichEdit1.SelStart := 2;
  RichEdit1.SelLength := 8;
  RichEdit1.SelAttributes.Color := clRed;
  s := copy(s,3,8);
  Y:= 0;
  for i := 1 to Length(s) do
    Y := Y +  Trunc(StrToInt(s[i])*Power(2, Length(s)-i));
  Label3.Caption := IntToStr(Y)+'('+IntToStr(Y-127)+')';
end;

procedure TForm1.RadioButton1Click(Sender: TObject);
begin
  Button1.Visible := True;
  Button2.Visible := False;
  Label8.Caption := 'Excess 127';
end;

procedure TForm1.RadioButton2Click(Sender: TObject);
begin
  Button1.Visible := False;
  Button2.Visible := True;
  Label8.Caption := 'Excess 1023';
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  x: Double;
  p: PDWORD;
  s: String;
  i: Integer;
  Y: Integer;
begin
  x := StrToFloat(Edit1.Text);
  p := @x;
  s := IntToBin(p^);
  while Length(s) < 32 do
    s := '0' + s;
  Edit2.Text := IntToHex(p^,8);
  Inc(p);
  s := IntToBin(p^)+s;
  Edit2.Text := IntToHex(p^,8) + Edit2.Text;
  while Length(s) < 64 do
    s := '0' + s;
  s := copy(s,1,1) + ' ' + copy(s,2,11) + ' ' + copy(s,13,52);
  RichEdit1.Text := s;
  RichEdit1.SelStart := 2;
  RichEdit1.SelLength := 11;
  RichEdit1.SelAttributes.Color := clRed;
  s := copy(s,3,11);
  Y:= 0;
  for i := 1 to Length(s) do
    Y := Y +  Trunc(StrToInt(s[i])*Power(2, Length(s)-i));
  Label3.Caption := IntToStr(Y)+'('+IntToStr(Y-1023)+')';
end;

procedure TForm1.Memo1Change(Sender: TObject);
var
  Str: String;
  i: Integer;
begin
  Edit1.OnChange := nil;
  Str := '';
  for i := 0 to Memo1.Lines.Count - 1 do
    Str := Str + Memo1.Lines.Strings[i];
  Edit1.Text :=FloatToStr(BinToFloat(Str));
  Edit1.OnChange := Edit1Change;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  RichEdit1.SelStart := 2;
  RichEdit1.SelLength := 8;
  RichEdit1.SelAttributes.Color := clRed;
end;

end.