A method for operating a machine control system having at least one ma-chine control (3, 3') for performing machine operations, having at least one machine (2, 2'), which is controlled via a control mechanism by the at least one machine controller (3, 3'), and having at least one mobile hand-held terminal, which is portable by an operator, for functionally influencing at least one of the machine controllers (3, 3'), which hand-held terminal has at least one operating element for manually influencing machine operations and at least one user interface having a display for monitoring or controlling the machine operations by an operator, and which hand-held terminal comprises at least one emergency stop actuation element for terminating potentially dangerous machine operations, wherein the respectively present actuation states of the at least one emergency stop actuation element, which actuation states may be manually activated or changed by an operator, are coupled via at least one transmission interface (6, 6') into an emergency stop safety circuit (9, 9') or into a safety bus system (22, 22') of the selected or actively connected machine controller (3, 3'), characterized by - schematically and/or abstractly up to photorealistically representing the machine control system or portions of the machine control system on the display of the hand-held terminal; - schematically representing the operational area(s) (W1, W2, W3, W4) of the at least one emergency stop actuation element at the hand-held terminal by means of the display of the hand-held terminal and additionally by means of selective, fail-safe controlling of at least one lighting means at the hand-held terminal and/or at least one discrete lighting means in or at the at least one emergency stop actuation element at the hand-held terminal, - wherein, for signaling the operational range(s) (W1, W2, W3, W4) of the at least one emergency stop actuation element, that schematically represented portion of the machine control system is graphically marked and/or highlighted in color or those schematically represented portions of the machine control system are graphically marked and/or highlighted in color on the display of the hand-held terminal for which portion(s) the emergency stop actuation element is functionally available. having at least one machine (2, 2'), which is controlled via a control mechanism by the at least one machine controller (3, 3'), and having at least one mobile hand-held terminal, which is portable by an operator, for functionally influencing at least one of the machine controllers (3, 3'), which hand-held terminal has at least one operating element for manually influencing machine operations and at least one user interface having a display for monitoring or controlling the machine operations by an operator, and which hand-held terminal comprises at least one emergency stop actuation element for terminating potentially dangerous machine operations, wherein the respectively present actuation states of the at least one emergency stop actuation element, which actuation states may be manually activated or changed by an operator, are coupled via at least one transmission interface (6, 6') into an emergency stop safety circuit (9, 9') or into a safety bus system (22, 22') of the selected or actively connected machine controller (3, 3'), characterized by - schematically and/or abstractly up to photorealistically representing the machine control system or portions of the machine control system on the display of the hand-held terminal; - schematically representing the operational area(s) (W1, W2, W3, W4) of the at least one emergency stop actuation element at the hand-held terminal by means of the display of the hand-held terminal and additionally by means of selective, fail-safe controlling of at least one lighting means at the hand-held terminal and/or at least one discrete lighting means in or at the at least one emergency stop actuation element at the hand-held terminal, - wherein, for signaling the operational range(s) (W1, W2, W3, W4) of the at least one emergency stop actuation element, that schematically represented portion of the machine control system is graphically marked and/or highlighted in color or those schematically represented portions of the machine control system are graphically marked and/or highlighted in color on the display of the hand-held terminal for which portion(s) the emergency stop actuation element is functionally available. - schematically and/or abstractly up to photorealistically representing the machine control system or portions of the machine control system on the display of the hand-held terminal; - schematically representing the operational area(s) (W1, W2, W3, W4) of the at least one emergency stop actuation element at the hand-held terminal by means of the display of the hand-held terminal and additionally by means of selective, fail-safe controlling of at least one lighting means at the hand-held terminal and/or at least one discrete lighting means in or at the at least one emergency stop actuation element at the hand-held terminal, - wherein, for signaling the operational range(s) (W1, W2, W3, W4) of the at least one emergency stop actuation element, that schematically represented portion of the machine control system is graphically marked and/or highlighted in color or those schematically represented portions of the machine control system are graphically marked and/or highlighted in color on the display of the hand-held terminal for which portion(s) the emergency stop actuation element is functionally available.