Matriz identidade

{ paulogp }
{ mac os 7 }
program Ada10p;

uses
    MemTypes, QuickDraw, OSIntf;

var
    i, j, n: integer;
    fim: string;

begin
    repeat
        clearscreen;
        writeln('Programa: Matriz Identidade!');
        writeln('============================');
        repeat
            writeln;
            write('Introduza um valor no intervalo ]0,20]: ');
            readln(n);
            writeln;
            if (n <= 0) or (n > 20)  then write('Atenção!!!');
        until (n > 0) and (n <= 20);
        writeln;
        for j:= 1 to n do
        begin
            for i:= 1 to n - 1 do
            begin
                if (i = j)  then write('   1');
                write('   0');
            end;
            if (j = n) then write('   1') else writeln;
        end;
        writeln;
        writeln;
        write('Repetir programa (S/N): ');
        readln(fim);
        uprstring(fim, true);
    until fim = 'N';
end.