아래 부분을....

void __fastcall TForm1::Button15Click(TObject *Sender) 
{ 
    double iValue1 = m_sInput.ToIntDef(0); 
    double iValue2 = m_sValue.ToIntDef(0); 
    double iCalc; 


    if     (m_sOper == "+") iCalc = iValue1 + iValue2; 
    else if(m_sOper == "-") iCalc = iValue1 - iValue2; 
    else if(m_sOper == "*") iCalc = iValue1 * iValue2; 
    else if(m_sOper == "/") iCalc = iValue2 / iValue1; 
            Panel3->Caption = iCalc; 

} 

이렇게 고치시면...

   double iValue1 = StrToFloat(m_sInput);
   double iValue2 = StrToFloat(m_sValue);
   ...
   ...
   ...
   Panel3->Caption = FormatFloat("0.0000000", iCalc);
  // 또는 Panel3->Caption = FloatToStr(iCalc);

될듯 합니다.




이재신 님이 쓰신 글 :
: //---------------------------------------------------------------------------
:
: #include <vcl.h>
: #pragma hdrstop
:
: #include "Unit12.h"
: //---------------------------------------------------------------------------
: #pragma package(smart_init)
: #pragma resource "*.dfm"
: TForm1 *Form1;
: //---------------------------------------------------------------------------
: __fastcall TForm1::TForm1(TComponent* Owner)
:     : TForm(Owner)
: {
:     m_sInput = "";
:
: }
: //---------------------------------------------------------------------------
:
: void __fastcall TForm1::Button1Click(TObject *Sender)
: {
:     TButton *pBtn =(TButton*)Sender;
:     m_sInput += pBtn->Caption;
:     Panel3->Caption = m_sInput;
:     Panel3->Font->Color = clRed;
:
: }
: //---------------------------------------------------------------------------
:
:
: void __fastcall TForm1::Button123Click(TObject *Sender)
: {
:     Panel3->Caption = m_sInput;
:     m_sInput = "";
:
: }
: //---------------------------------------------------------------------------
:
:
:
:
: void __fastcall TForm1::Button12Click(TObject *Sender)
: {
:
:    m_sValue = m_sInput;
:    m_sInput = "";
:    Panel3->Caption = m_sInput;
:    m_sOper = "+";
:
:
: }
: //---------------------------------------------------------------------------
:
: void __fastcall TForm1::Button15Click(TObject *Sender)
: {
:     double iValue1 = m_sInput.ToIntDef(0);
:     double iValue2 = m_sValue.ToIntDef(0);
:     double iCalc;
:
:
:     if     (m_sOper == "+") iCalc = iValue1 + iValue2;
:     else if(m_sOper == "-") iCalc = iValue1 - iValue2;
:     else if(m_sOper == "*") iCalc = iValue1 * iValue2;
:     else if(m_sOper == "/") iCalc = iValue2 / iValue1;
:             Panel3->Caption = iCalc;
:
: }
: //---------------------------------------------------------------------------
:
: void __fastcall TForm1::Button13Click(TObject *Sender)
: {
:     m_sValue = m_sInput;
:     m_sInput = "";
:     Panel3->Caption = m_sInput;
:     m_sOper = "-";
:
: }
: //---------------------------------------------------------------------------
:
: void __fastcall TForm1::Button14Click(TObject *Sender)
: {
:    m_sValue = m_sInput;
:    m_sInput = "";
:    Panel3->Caption =m_sInput;
:    m_sOper = "*";
: }
: //---------------------------------------------------------------------------
:
: void __fastcall TForm1::Button17Click(TObject *Sender)
: {
:     m_sValue = m_sInput;
:     m_sInput = "";
:     Panel3->Caption =m_sInput;
:     m_sOper = "/";
: }
: //---------------------------------------------------------------------------
:
: void __fastcall TForm1::Button11Click(TObject *Sender)
: {
:     m_sInput = m_sInput.SubString(1,m_sInput.Length()-1);
:     Panel3->Caption = m_sInput;
:
:
:
: }
: //---------------------------------------------------------------------------
:
:
:
:
: 볼랜드 6.0으로 하고 있는데 소수점 까지 계산을 할려고 하는데 어떻게 해야될지좀 알려 줗세요