Computers as Components, 2nd Edition

5.2 Models of Programs 215

/* update the tail */

tail = wrap(tail);

/* add val to the tail of the queue */

q[tail] = val;

}

And here is the code for removing an element from the head of the queue, known as

dequeueing:

int dequeue() {

int returnval; /* use this to remember the value that

you will return */

/* check for an empty queue */

if (head == wrap(tail)) error(DEQUEUE_ERROR);

/* remove from the head of the queue */

returnval = q[head];

/* update head */

head = wrap(head);

/* return the value */

return returnval;

}

5.2 MODELS OF PROGRAMS

In this section, we develop models for programs that are more general than source

code. Why not use the source code directly? ...