Parameter input routine

WHILE (NOT All_parms) AND (Parm_exist) AND (Parm_Ok) DO BEGIN
    Check_parm;
    IF Parm_Ok THEN BEGIN
        IF All_parms THEN BEGIN
            Perform_cmd;
        END ELSE { IF NOT All_parms THEN } BEGIN
            IF NOT Parm_asked_for THEN BEGIN
                Ask_for_parm;
            END ELSE { IF Parm_asked_for THEN } BEGIN
                IF DefaultValue THEN BEGIN
                    Get_default_parm;
                END ELSE { IF NOT DefaultValue THEN } BEGIN
                    OpCmdErrHandler( Too_few_parms );    
                END;
            END;
        END;
    END ELSE { IF NOT Parm_Ok THEN } BEGIN
        OpCmdErrHandler( Invalid_cmd );
END; { WHILE }