procedure setOrder (fieldlist : String);

Function setOrder() sets order of records by some field or list of fields.
The function does not change a file, it re-orders records in a memory.
One function accepts a string with fields delimited by comma, another function accepts an array.
To return the original order of records - call unserOrder().
function descendingMode() set either ascending or descending order.

procedure setOrderA(fields : array of String);
procedure unsetOrder;
procedure descendingMode(descending : Boolean);

begin
    // your code
    dbf.setOrder('FIRSTNAME,LASTNAME');
    dbf.descendingMode(True);
    dbf.setOrderA( ('FIRSTNAME', 'LASTNAME') );
    // your code
    dbf.unsetOrder;
end;