MCDU or "Multifunction Control and Display Unit" is the heart of modern aircraft, from which the pilot will enter details about a given flight.
The MCDU usually has access to all systems in the aircraft.

From the AM4 MCDU it is possible to perform various task, such as purchasing fuel, renaming registrations, changing cost index, departing flights and lookup routes.
Please note that the MCDU may not work well on smaller mobile devices.

To use the MCDU, click the line select key next to the section you want to access.
For example Airport (ARPT).
To lookup an airport, enter the icao or iata code using the keypad.
Once entered, click the line select key next to the orange boxes, to move the entry into position.
The MCDU will look up that airport and return information about it, if any.

You can also look up a route by entering both iata/icao codes.
For example: CPH/CDG
Moving this into position will look up the route and return demand data about this route, as well as distance and runway information.

It is also possible to view a pax manifest from the MCDU.
Click Routes (RTS) and then the selected flight.
If the aircraft is airborne, you will see a selection called “Manifest”. Clicking the line select key next to this, will return the pax manifest for the given flight.