Nassi-Shneiderman structograms

Nassi-Shneiderman structogram: the full guide

A structogram (Nassi-Shneiderman diagram, NSD) shows an algorithm as nested boxes with no arrows. The whole logic reads top to bottom as a single block, which is why it is often required as an alternative to a flowchart. Below: every block shown visually, a live example, and how to build one from code in seconds.

Bubble sort as a Nassi-Shneiderman structogram: nested blocks instead of arrows.

The three building blocks

Any algorithm is these three, nested inside one another. No arrows — nesting shows the control flow directly.

Read x

y = x * 2

Print y

Sequence

Actions one after another — a stack of boxes, top to bottom.

x > 0?

YesNo

sign = +

sign = −

Branch

A condition splits into two columns, “Yes” on the left and “No” on the right.

while i < n

sum = sum + i

Loop

A frame wraps the repeated body on the top and left side.

A live example

Grading a score — a branch nested after an input. This is exactly what rombik outputs from code.

grade

Input score

score ≥ 90?

YesNo

Print «Excellent»

Print «Other»

Structogram vs flowchart

Same logic, two views. A structogram is more compact and arrow-free; a flowchart is more familiar to graders. rombik builds both from the same code — flip one toggle.

Flowchart per ISO 5807 — the full guide →

Make a structogram from code

Paste code in any of 10 languages, flip the “Structogram” toggle, and export to Word, Visio, draw.io, Typst, Excalidraw, SVG, PNG, JPEG, WebP, GIF, PDF or HTML as native objects.

Make a structogram