In structured modeling, what is a key characteristic of a Nassi-Schneiderman (structogram) chart?

Introduction / Context:
Nassi-Schneiderman charts, also called structograms, offer a diagrammatic way to depict structured programming constructs without arbitrary jumps. They provide a clean alternative to traditional flowcharts by emphasizing nested, block-structured control flow aligned with sequence, selection, and repetition.

Given Data / Assumptions:

• We are modeling structured (block) control flow.
• Overlapping or unstructured constructs (such as arbitrary GOTO) are discouraged.
• The chart should reflect nesting directly.

Concept / Approach:
Structograms use nested rectangles (boxes within boxes). Each block corresponds to a control structure: a simple rectangle for sequence, a split block for selection, and a looping block for repetition. This nested form directly mirrors structured code blocks, improving readability and eliminating crossing lines common in complex flowcharts.

Step-by-Step Solution:

Verification / Alternative check:
Flowcharts often show arrows and may become tangled; structograms avoid overlaps by construction, reinforcing structured programming principles.

Why Other Options Are Wrong:

Common Pitfalls:
Trying to depict unstructured jumps or spaghetti logic in structograms defeats their purpose.

Final Answer:
They are composed of boxes within boxes that represent sequence, selection, and repetition.