108 ◾ Computational Thinking for the Modern Problem Solver
e second step in top-down design is to consider each of the instruc-
tions from the top level and one by one rene each instruction into parts.
In our o-road vehicle example, drawing the grill involves headlights
and black grill openings that can be included to provide more detail.
Similarly, the tires, windshield, and auxiliary lights can be further rened.
Figure4.10 shows a suitable second-level algorithm.
Notice that top-down design produces an algorithm that is very much
like an outline. Instructions from higher levels are rened into more
detailed instructions that are indented beneath. We have chosen to num-
ber the algorithm parts a little dierently than standard ou ...