An interface can be identified by a GUID. This is a 128-bit number, which is represented in a text representation (a string literal):
['{HHHHHHHH-HHHH-HHHH-HHHH-HHHHHHHHHHHH}']
Each H character represents a hexadecimal number (0–9, A–F). The format contains 8-4-4-4-12 numbers. A GUID can also be represented by the following record, defined in the objpas unit (included automatically when in DELPHI or OBJFPC mode):
PGuid = ^TGuid;
TGuid = packed record
case integer of
1 : (
Data1 : DWord;
Data2 : word;
Data3 : word;
Data4 : array[0..7] of byte;
);
2 : (
D1 : DWord;
D2 : word;
D3 : word;
D4 : array[0..7] of byte;
);
3 : ( { uuid fields according to RFC4122 }
time_low : dword;
time_mid : word;
time_hi_and_version : word;
clock_seq_hi_and_reserved : byte;
clock_seq_low : byte;
node : array[0..5] of byte;
);
end;
A constant of type TGUID can be specified using a string literal:
{$mode objfpc}
program testuid;
Const
MyGUID : TGUID = '{10101010-1010-0101-1001-110110110110}';
begin
end.
Normally, the GUIDs are only used in Windows, when using COM interfaces. More on this in the next section.