function codec(action)
%CODEC  Coder/Decoder
%   The CODEC acts like an encoder/decoder for  
%   messages using the letters of the alphabet.   
%   The "Code" popup menu determines the          
%   degree of transposition: a "b" code transposes
%   all letters by one like so: "alphabet" becomes
%   "bmqibcfu" and so on.                         
%
%   The "Mode" popup menu determines whether      
%   you are encoding or decoding.                  

%   Ned Gulley, 6-21-93; jae Roh, 10-15-96
%   Copyright 1984-2003 The MathWorks, Inc.
%   $Revision: 5.11.4.2 $  $Date: 2004/04/10 23:24:27 $

% Possible actions:
% initialize
% type
% shading
% colormap
% axis

if nargin<1,
   action='initialize';
end;

if strcmp(action,'initialize'),
   figNumber=figure( ...
      'Visible','off', ...
      'Name','Code/Decode', ...
      'NumberTitle','off');
   
   %===================================
   % Set up the Input Window
   top=0.95;
   left=0.05;
   right=0.75;
   bottom=0.53;
   labelHt=0.05;
   spacing=0.005;
   callback='codec(''encode'')';
   
   % First, the MiniCommand Window frame
   frmBorder=0.02;
   frmPos=[left-frmBorder bottom-frmBorder ...
         (right-left)+2*frmBorder (top-bottom)+2*frmBorder];
   uicontrol( ...
      'Style','frame', ...
      'Units','normalized', ...
      'Position',frmPos, ...
      'BackgroundColor',192/255*[1 1 1]);
   % Then the text label
   labelPos=[left top-labelHt (right-left) labelHt];
   uicontrol( ...
      'Style','text', ...
      'Units','normalized', ...
      'Position',labelPos, ...
      'BackgroundColor',192/255*[1 1 1], ...
      'String','Input');
   % Then the editable text field
   txtPos=[left bottom (right-left) top-bottom-labelHt-spacing];
   inputHndl=uicontrol( ...
      'Style','edit', ...
      'FontName','courier', ...
      'FontSize',14, ...
      'HorizontalAlignment','left', ...
      'Units','normalized', ...
      'Max',10, ...
      'String','MATLAB', ...
      'BackgroundColor',[1 1 1], ...
      'Callback',callback, ...
      'Position',txtPos);
   
   %===================================
   % Set up the Output Window
   top=0.48;
   left=0.05;
   right=0.75;
   bottom=0.05;
   labelHt=0.05;
   spacing=0.005;
   % First, the MiniCommand Window frame
   frmBorder=0.02;
   frmPos=[left-frmBorder bottom-frmBorder ...
         (right-left)+2*frmBorder (top-bottom)+2*frmBorder];
   uicontrol( ...
      'Style','frame', ...
      'Units','normalized', ...
      'Position',frmPos, ...
      'BackgroundColor',192/255*[1 1 1]);
   % Then the text label
   labelPos=[left top-labelHt (right-left) labelHt];
   uicontrol( ...
      'Style','text', ...
      'Units','normalized', ...
      'Position',labelPos, ...
      'BackgroundColor',192/255*[1 1 1], ...
      'String','Output');
   % Then the editable text field
   txtPos=[left bottom (right-left) top-bottom-labelHt-spacing];
   outputHndl=uicontrol( ...
      'Style','edit', ...
      'FontName','courier', ...
      'FontSize',14, ...
      'HorizontalAlignment','left', ...
      'Units','normalized', ...
      'Max',10, ...
      'BackgroundColor',[1 1 1], ...
      'Position',txtPos);
   % Save this handle for future use
   %set(gcf,'UserData',txtHndl);
   
   %====================================
   % Information for all buttons
   labelColor=[0.8 0.8 0.8];
  % yInitLabelPos=0.80;
   xLabelPos=0.80;
   labelWid=0.15;
   labelHt=0.05;
   btnWid=0.15;
   btnHt=0.05;
   % Spacing between the label and the button for the same command
   btnOffset=0.005;
   % Spacing between the button and the next command's label
   spacing=0.05;
   
   %====================================
   % The CONSOLE frame
   frmBorder=0.02;
   yPos=0.05-frmBorder;
   frmPos=[xLabelPos-frmBorder yPos btnWid+2*frmBorder 0.9+2*frmBorder];
   uicontrol( ...
      'Style','frame', ...
      'Units','normalized', ...
      'Position',frmPos, ...
      'BackgroundColor',192/255*[1 1 1]);
   
   %====================================
   % The CODE command popup button
   btnNumber=1;
   yLabelPos=0.95-(btnNumber-1)*(btnHt+labelHt+spacing);
   labelStr=' Code Key Letter';
   popupStr=char(97:122)';
   callbackStr='codec(''encode'')';
   
   % Generic label information
   labelPos=[xLabelPos yLabelPos-labelHt labelWid labelHt];
   uicontrol( ...
      'Style','text', ...
      'Units','normalized', ...
      'Position',labelPos, ...
      'BackgroundColor',labelColor, ...
      'HorizontalAlignment','left', ...
      'String',labelStr);
   
   % Generic popup button information
   btnPos=[xLabelPos yLabelPos-labelHt-btnHt-btnOffset btnWid btnHt];
   typeHndl=uicontrol( ...
      'Style','popup', ...
      'Units','normalized', ...
      'Position',btnPos, ...
      'Value',2, ...
      'String',popupStr, ...
      'Callback',callbackStr);
   
   %====================================
   % The MODE command popup button
   btnNumber=2;
   yLabelPos=0.95-(btnNumber-1)*(btnHt+labelHt+spacing);
   labelStr=' Mode';
   popupStr=str2mat('Encode','Decode');
   callbackStr='codec(''encode'')';
   
   % Generic label information
   labelPos=[xLabelPos yLabelPos-labelHt labelWid labelHt];
   uicontrol( ...
      'Style','text', ...
      'Units','normalized', ...
      'Position',labelPos, ...
      'BackgroundColor',labelColor, ...
      'HorizontalAlignment','left', ...
      'String',labelStr);
   
   % Generic popup button information
   btnPos=[xLabelPos yLabelPos-labelHt-btnHt-btnOffset btnWid btnHt];
   modeHndl=uicontrol( ...
      'Style','popup', ...
      'Units','normalized', ...
      'Position',btnPos, ...
      'String',popupStr, ...
      'Callback',callbackStr);
   
   %====================================
   uicontrol( ...
      'Style','push', ...
      'Units','normalized', ...
      'Position',[xLabelPos 0.20 btnWid 0.10], ...
      'String','Info', ...
      'Callback','codec(''info'')');
   
   % The close button.
   uicontrol( ...
      'Style','push', ...
      'Units','normalized', ...
      'Position',[xLabelPos 0.05 btnWid 0.10], ...
      'String','Close', ...
      'Callback','close(gcf)');
   
   % Uncover the figure
   hndlList=[inputHndl outputHndl typeHndl modeHndl];
   set(figNumber,'Visible','on', ...
      'UserData',hndlList);
   codec encode
   
elseif strcmp(action,'info'),
   helpwin(mfilename);
   
elseif strcmp(action,'encode'),
   hndlList=get(gcf,'UserData');
   inputHndl=hndlList(1);
   outputHndl=hndlList(2);
   typeHndl=hndlList(3);
   modeHndl=hndlList(4);
   % Get direction
   dir=get(modeHndl,'Value')*(-2)+3;
   % Get key
   key=get(typeHndl,'Value');
   inStr=get(inputHndl,'String');
   inStr=abs(inStr);
   selectLowerCase=(inStr>=97)&(inStr<=122);
   selectUpperCase=(inStr>=65)&(inStr<=90);
   codeStrLower=inStr(selectLowerCase)+dir*(key-1);
   codeStrUpper=inStr(selectUpperCase)+dir*(key-1);
   if ~isempty(codeStrLower),
      codeStrLower(codeStrLower>122)=codeStrLower(codeStrLower>122)-26;
      codeStrLower(codeStrLower<97)=codeStrLower(codeStrLower<97)+26;
   end;
   if ~isempty(codeStrUpper),
      codeStrUpper(codeStrUpper>90)=codeStrUpper(codeStrUpper>90)-26;
      codeStrUpper(codeStrUpper<65)=codeStrUpper(codeStrUpper<65)+26;
   end;
   if ~isempty(inStr),
      inStr(selectLowerCase)=codeStrLower;
      inStr(selectUpperCase)=codeStrUpper;
   end;
   outStr=char(inStr);
   set(outputHndl,'String',outStr);
   
end;    % if strcmp(action, ...