How does GetWindowsName get the name and version of the current operating system?

Unit GetWindowsName;

Interface
Uses Registry, Windows, ShellAPI;
{--------------------------------------------------------------------------}
{1. Obtain the current Windows Version}
Const
COsUnknown =-1;
COsWin95 = 0;
COsWin98 = 1;
COsWin98SE = 2;
COsWinME = 3;
COsWinNT = 4;
COsWin2000 = 5;
COsXP = 6;
Function GetWindowsVersion: string;
Function GetOperatingSystem: Integer;
Function IsXP: Boolean;
Function IsWin2000: Boolean;
Function IsWin95: Boolean;
Function IsWinME: Boolean;
Function IsWinNT2: Boolean;

Implementation
Function GetOperatingSystem: Integer;
Var
OsVerInfo: TOSVersionInfo;
MajorVer, minorVer: Integer;
Begin
Result: = cOsUnknown;
{Set operating system type flag}
OsVerInfo. dwOSVersionInfoSize: = SizeOf (TOSVersionInfo );
If GetVersionEx (osVerInfo) then
Begin
MajorVer: = osVerInfo. dwMajorVersion;
MinorVer: = osVerInfo. dwMinorVersion;
Case osVerInfo. dwPlatformId
VER_PLATFORM_WIN32_NT: {Windows NT/2000}
Begin
If majorVer Result: = cOsWinNT
Else if (majorVer = 5) and (minorVer = 0) then
Result: = cOsWin2000
Else if (majorVer = 5) and (minorVer = 1) then
Result: = cOsXP
Else
Result: = cOsUnknown;
End;
VER_PLATFORM_WIN32_WINDOWS: {Windows 9x/ME}
Begin
If (majorVer = 4) and (minorVer = 0) then
Result: = cOsWin95
Else if (majorVer = 4) and (minorVer = 10) then
Begin
If osVerInfo. szCSDVersion [1] = 'A' then
Result: = cOsWin98SE
Else
Result: = cOsWin98;
End
Else if (majorVer = 4) and (minorVer = 90) then
Result: = cOsWinME
Else
Result: = cOsUnknown;
End;
Else
Result: = cOsUnknown;
End;
End
Else
Result: = cOsUnknown;
End;

{--------------------------------------------------------------------------}
{2. Determine whether the current OS belongs to that one}
Function IsXP: Boolean;
Var
OS: TOSVERSIONINFO;
Begin
OS. dwOSVersionInfoSize: = SizeOf (TOSVERSIONINFO );
GetVersionEx (OS );
Result: = (OS. dwPlatformId = VER_PLATFORM_WIN32_NT) and
(OS. dwMajorVersion = 5) and (OS. dwMinorVersion = 1 );
End;

Function IsWin2000: Boolean;
Var
OS: TOSVersionInfo;
Begin
ZeroMemory (@ OS, SizeOf (OS ));
OS. dwOSVersionInfoSize: = SizeOf (OS );
GetVersionEx (OS );
Result: = (OS. dwMajorVersion> = 5) and
(OS. dwPlatformId = VER_PLATFORM_WIN32_NT );
End;

Function IsWinNT2: Boolean;
Var
OS: TOSVersionInfo;
Begin
ZeroMemory (@ OS, SizeOf (OS ));
OS. dwOSVersionInfoSize: = SizeOf (OS );
GetVersionEx (OS );
Result: = OS. dwPlatformId = VER_PLATFORM_WIN32_NT;
End;

{Or :}

{Function IsWinNT2: Boolean;
Begin
Result: = Win32Platform = VER_PLATFORM_WIN32_NT;
End ;}

Function IsWinME: Boolean;
Var
OS: TOSVersionInfo;
Begin
ZeroMemory (@ OS, SizeOf (OS ));
OS. dwOSVersionInfoSize: = SizeOf (OS );
GetVersionEx (OS );
Result: = (OS. dwMajorVersion = 4) and (OS. dwMinorVersion = 90) and
(OS. dwPlatformId = VER_PLATFORM_WIN32_WINDOWS );
End;

Function IsWin95: Boolean;
VaR
OS: tosversioninfo;
Begin
Zeromemory (@ OS, sizeof (OS ));
OS. dwosversioninfosize: = sizeof (OS );
Getversionex (OS );
Result: = (OS. dwmajorversion> = 4) and (OS. dwminorversion = 0) and
(OS. dwplatformid = ver_platform_win32_windows );
End;
Function getwindowsversion: string;
VaR
Verinfo: tosversioninfo;
Platformid, versionnumber: string;
Reg: Tregistry;
Begin
Verinfo. dwosversioninfosize: = sizeof (verinfo );
Getversionex (verinfo );
// Detect Platform
Reg: = Tregistry. Create;
Reg. rootkey: = HKEY_LOCAL_MACHINE;
Case VerInfo. dwPlatformId
VER_PLATFORM_WIN32s:
Begin
// Registry (Huh? What registry ?)
PlatformId: = 'windows 3.1 ';
End;
VER_PLATFORM_WIN32_WINDOWS:
Begin
// Registry
Reg. OpenKey ('/SOFTWARE/Microsoft/Windows/currentversion', False );
PlatformId: = Reg. ReadString ('productname ');
VersionNumber: = Reg. ReadString ('versionnumber ');
End;
VER_PLATFORM_WIN32_NT:
Begin
// Registry
Reg. OpenKey ('/SOFTWARE/Microsoft/Windows NT/currentversion', False );
PlatformId: = Reg. ReadString ('productname ');
VersionNumber: = Reg. ReadString ('currentversion ');
End;
End;
Reg. Free;
Result: = PlatformId + '(version' + VersionNumber + ')';
End;

End.