Delphi

This code demonstrates use of windows registery and function overloading to read from registery:
if key doesnt exist it's created and Default passed to key value ReadReg(KeyToRead,DefaultValue)
to write to registery:
writereg(KeyToWrite,ValueToKey)
Supports integer,string and boolean types, other type can be similary added.}

unit module1;

interface

uses Windows, registry;

function WriteReg(Key:string;value:integer) :boolean; overload;
function WriteReg(Key:string;value:boolean) :boolean; overload;
function WriteReg(Key:string;value:String) :boolean; overload;
function ReadReg(Key:string;default:String='') :string; overload;
function ReadReg(Key:string;default:integer=0) :integer; overload;
function ReadReg(Key:string;default:boolean=false):boolean;overload;

const
ApplicationName:string ='MyProgram'; //Your Programname

implementation

function ReadReg(Key:string;default:integer=0):integer;
var
Registry: TRegistry;
begin
Registry :=TRegistry.Create;
Registry.RootKey :=HKEY_CURRENT_USER;
Registry.OpenKey('\software\'+ ApplicationName,True);
if registry.ValueExists(key) =true then
result:=Registry.readinteger(key)
else
begin
Registry.Writeinteger(key,default);
result:=Registry.readinteger(key);
end;
Registry.Free;
end;

function ReadReg(Key:string;default:string=''):string;
var
Registry : TRegistry;
begin
Registry := TRegistry.Create;
Registry.RootKey :=HKEY_CURRENT_USER;
Registry.OpenKey('\software\'+ApplicationName,True);
if registry.ValueExists(key) then
readreg := Registry.readstring(key)
else
begin
Registry.Writestring(key,default);
Readreg := Registry.readstring(key);
end;
Registry.Free;
end;


function ReadReg(Key:string;default:boolean=false):boolean;
var
Registry: TRegistry;
begin
Registry := TRegistry.Create;
Registry.RootKey := HKEY_CURRENT_USER;
Registry.OpenKey('\software\'+ApplicationName,True);
if registry.ValueExists(key) then
readreg:=Registry.readbool(key)
else
begin
Registry.Writebool(key,default);
readreg:=Registry.readbool(key);
end;
Registry.Free;
end;

function WriteReg(Key:string;value:boolean):boolean;
var Registry: TRegistry;
begin
Registry:=TRegistry.Create;
Registry.RootKey:=HKEY_CURRENT_USER;
Registry.OpenKey('\software\'+ApplicationName,True);
registry.WriteBool(key,value);
result:= registry.KeyExists(key);
Registry.Free;
end;

function WriteReg(Key:string;value:string):boolean;
var
Registry: TRegistry;
begin
Registry := TRegistry.Create;
Registry.RootKey := HKEY_CURRENT_USER;
Registry.OpenKey('\software\'+ApplicationName,True);
registry.Writestring(key,value);
result:= registry.KeyExists(key);
Registry.Free;
end;

function WriteReg(Key:string;value:integer):boolean;
var
Registry: TRegistry;
begin
Registry := TRegistry.Create;
Registry.RootKey := HKEY_CURRENT_USER;
Registry.OpenKey('\software\'+ApplicationName,True);
registry.Writeinteger(key,value);
writereg:= registry.KeyExists(key);
Registry.Free;
end;

Compare dates

Uses SysUtils;
...
if(Date < EncodeDate( 2000, 1, 1 )) then
Showmessage(' The date is ' + DateToStr(Date));
…