   ______________263

  ,     ,   Key, -
|      .   ,    -
'       ,    , a char  .   -
       ,  ,  
 ,   ,  , ,  .
        .

, ,    ,     -
  Ļ  Ļ (),   ͻ   ().  -
      OnKeyPress  :

if ((Key == '') II (Key == '')) ...

       -
,       .    -
      switch (. -
 11.8.1.2   II):

switch (Key)
{
case '':

case '': ... ;

break;

case '':

case '': ...;

break;

default: Beep() ;

)

       , 
     .

     ,   ,
  Key   .     
Key,       , 
I          -
. , ,        Editi,  -
        .  
  ,      
, ,  :

Set <char, '0', '9'> Dig;

Dig  '0'  '  '2'  '3'  '4'  '5'
 '6'  '7'  '8'  '9';

if ( ! Dig.Contains(Key))
{ Key = 0;  () ; }

    ,    , -
          -
,    ,      .
       
 .

4.4     
Drag&Drop

         
 (Drag&Drop),   ,   -
  Windows. ,      ,
  ,     ,  .. ,  -
       C++Builder.