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Tarea 1:

Solve the problem of producer/consumer fixed size buffer using shared memory 
and counting semaphores. Your program must be designed to work continuously, 
but would be compiled for say 50 messages. A simple floating point number
for each message would be fine. You should make the size of the buffer and 
the number of messages to be transmitted defined in a header file. You
should use usleep() to simulate a slow consumer and a slow producer to test
both extremes. It should be possible for the consumer and producer to access 
the buffer simultaneously, as long as it is not full or empty.

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Tarea 2: 

Solve the multiple reader / multiple writer problem.

You should give priority to writers, so that as soon as a writer arrives, ALL
arriving readers will have to wait, but all that have already entered can 
continue. 

When a reader enters, he must check to see if there are any writers, and if so,
put himself to sleep, otherwise, enter immediately.

When a writer enters, he must check to see if there are other writers or reader,
and if so put himself to sleep.

When a reader leaves, he must see if he is the last reader inside, and if so
check for waiting writers, and wake one up if there is at least one.

A writer on leaving, must check to see if there is another writer waiting, and if so
wake one up, if not wake up ALL waiting readers. 
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