freepascal.compiler/docs/sysutex/ex92.pp

{$h+}
program example92;

{ This program demonstrates the
  GetEnvironmentVariableCount function }

uses sysutils;

Var
  I : Integer;

begin
  For I:=1 to GetEnvironmentVariableCount do
    Writeln(i:3,' : ',GetEnvironmentString(i));
end.