C / C++ / MFC

char szText [256];

GetWindowText (hWnd1, szText, 256);
if (strlen (szText) < 255)
{
    strcat (szText, "A"); //add new letter
    SetWindowText (hWnd2, szText);
}
else
    ; // OMG, not enough room to add another character

int    iLen;

HWND hEdit1 = ::DlgGetItem(hDlg, ID_EDIT1);
iLen = ::GetWindowTextLength(hEdit1);
// Test if the length of the text is zero, if it is, then there is nothing to do.
if (iLen < 0)
{
  return;
}

TCHAR *pszText;
// Allocate memory for your text.
pszText = new TCHAR[iLen+1];
// Verify your memory allocation.
if (NULL == pszText)
{
  return;
}
// Get the text from the first edit box.
::GetWindowText(hEdit1, pszText, iLen+1);
// Set the text into the 2nd edit box.  I am using pointer arithmatic to set the pointer 
// to the second character in the string.
HWND hEdit2 = ::GetDlgItem(hDlg, ID_EDIT2);
::SetWindowText(hEdit2, pszText + 1);

5, "hello", "my", "friends", 10