August 1999
AP207 : ADVANCED PROGRAMMING TECHNIQUES

QUESTION 4

Total Marks: 20 Marks

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for Question 4
You are to implement an Air Traffic Control queueing system. When a flight reaches the airport, it recives a landing_number which identifies its position in the landing queue. The following data type is used to represent the landing queue:

TYPE airline = (BritishAirways, SingaporeAirlines, KLM, Lufthansa);

aeroplane = RECORD

owner : airline;
flight_number : String[10];
airtimeleft : Integer;
landing_number : Integer;

END;

NodeType = ^Node;
Node = RECORD

next : NodeType;
data : aeroplane;

END;

QueueType = RECORD

front : NodeType;
rear : NodeType;

END;

In QueueType, front points to the first aeroplane in the queue and rear points to the last aeroplane in the queue. The Next field of a node points from the older aeroplane in the queue to the newer aeroplane. In addition to this, it is also needed to know how much fuel an aeroplane has left, in case it is about to run out, and this airtime_left is measured in minutes.

 
(a) Write a function, the prototype of which is given below, which takes the landing queue and removes and returns the oldest aeroplane in the landing queue (the one at the front).

FUNCTION LandPlane (VAR queue: QueueType) : aeroplane;

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(b) Write a function the prototype of which is given below, that returns the landing_number of the aeroplane with the least fuel left in the queue (i.e., the least airtime left). If there are no aeroplanes in the queue, the function should return 0.
FUNCTION LeastFuelLeft(queue: QueueType) : Integer;

 

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(c) A takeoff queue is represented by the same QueueType, where airtimeleft represents time remaining until takeoff; and landing_number represents the place in the takeoff queue.

Implement the procedure TakeOffPlane, which takes the takeoff queue and an aeroplanes details, and adds it to the takeoff queue. Note that you will need to calculate the landing_number for the aeroplane, by adding one to the landing number of the oldest aeroplane in the queue.

PROCEDURE TakeOffPlane (VAR queue: QueueType, TimeToTakeOff : Integer);

 

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(d) Write a function called CoordinateQueue, which will take 3 arguments: the landing queue, the takeoff queue and a time in minutes.

The function should land the oldest aeroplane in the queue, and set it up for takeoff in the takeoff queue, with the time parameter specifying the time in minutes until the plane is expected to take off. The function will return TRUE if there has been a place to land and schedule for takeoff, and FALSE otherwise.

 

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