function Format ( Const Formatting : string; Const Data : array of const ) : string;
function Format ( Const Formatting : string; Const Data : array of const; FormatSettings : TFormatSettings ) : string;

result := Format('Decimal = %d', [-123])

Provides C formatting: %[Index:][-][Width][.Precision]Type

%d	Decimal (integer)
%e	Scientific
%f	Fixed
%g	General
%m	Money
%n	Number (floating)
%p	Pointer
%s	String
%u	Unsigned decimal
%x	Hexadecimal