Как написать код для нахождения процентов от числа?
#include "stdafx.h"
#include "kalkulyator.h"
#include "kalkulyatorDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#endif


// CAboutDlg dialog used for App About

class CAboutDlg : public CDialog
{
public:
CAboutDlg();

// Dialog Data
enum { IDD = IDD_ABOUTBOX };

protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support

// Implementation
protected:
DECLARE_MESSAGE_MAP()
};

CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
}

void CAboutDlg:oDataExchange(CDataExchange* pDX)
{
CDialog:oDataExchange(pDX);
}

BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
END_MESSAGE_MAP()


// CkalkulyatorDlg dialog




CkalkulyatorDlg::CkalkulyatorDlg(CWnd* pParent /*=NULL*/)
: CDialog(CkalkulyatorDlg::IDD, pParent)
, a(0)
, b(0)
, c(0)
{
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

void CkalkulyatorDlg:oDataExchange(CDataExchange* pDX)
{
CDialog:oDataExchange(pDX);
DDX_Text(pDX, IDC_EDIT1, a);
DDX_Text(pDX, IDC_EDIT2, b);
DDX_Text(pDX, IDC_EDIT3, c);
}

BEGIN_MESSAGE_MAP(CkalkulyatorDlg, CDialog)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
//}}AFX_MSG_MAP
ON_BN_CLICKED(IDC_BUTTON1, &CkalkulyatorDlg::OnBnClickedButton1)
ON_BN_CLICKED(IDC_BUTTON2, &CkalkulyatorDlg::OnBnClickedButton2)
ON_BN_CLICKED(IDC_BUTTON3, &CkalkulyatorDlg::OnBnClickedButton3)
ON_BN_CLICKED(IDC_BUTTON4, &CkalkulyatorDlg::OnBnClickedButton4)
ON_BN_CLICKED(IDC_BUTTON5, &CkalkulyatorDlg::OnBnClickedButton5)
END_MESSAGE_MAP()


// CkalkulyatorDlg message handlers

BOOL CkalkulyatorDlg::OnInitDialog()
{
CDialog::OnInitDialog();

// Add "About..." menu item to system menu.

// IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000);

CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
}

// Set the icon for this dialog. The framework does this automatically
// when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon

// TODO: Add extra initialization here

return TRUE; // return TRUE unless you set the focus to a control
}

void CkalkulyatorDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}

// If you add a minimize button to your dialog, you will need the code below
// to draw the icon. For MFC applications using the document/view model,
// this is automatically done for you by the framework.

void CkalkulyatorDlg::OnPaint()
{
if (IsIconic())
{
CPaintDC dc(this); // device context for painting

SendMessage(WM_ICONERASEBKGND, reinterpret_cast(dc.GetSafeHdc()), 0);

// Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2;

// Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}

// The system calls this function to obtain the cursor to display while the user drags
// the minimized window.
HCURSOR CkalkulyatorDlg::OnQueryDragIcon()
{
return static_cast(m_hIcon);
}


void CkalkulyatorDlg::OnBnClickedButton1()
{
UpdateData(true);
c=a+b;
UpdateData(false);
}

void CkalkulyatorDlg::OnBnClickedButton2()
{
UpdateData(true);
c=a-b;
UpdateData(false);
}

void CkalkulyatorDlg::OnBnClickedButton3()
{
UpdateData(true);
c=a*b;
UpdateData(false);
}

void CkalkulyatorDlg::OnBnClickedButton4()
{
UpdateData(true);
с=a/b;
UpdateData(false);
}

void CkalkulyatorDlg::OnBnClickedButton5()
{
UpdateData(true);
c=a%b;
UpdateData(false);
}