$monitor keeps displaying the values of its arguments whenever one of that changes. i.e., whenever values of d, select or q changes, it displays the value in the output window. Using a for loop, I have changed value of d from 0000 to 1111, and in each case change the value of select to all possible values. A part of output is as displayed the diagram in the right.
Note that if we use for( d = 0; d