Flowchart Symbols

A flowchart is a diagram of an algorithm's control flow. It carries the same information as pseudocode in visual form, and it is often easier to follow when the logic branches heavily.

The syllabus is explicit that flowcharts here are only for visualising control flow, and suggests the RAPTOR tool for drawing and running them.

The symbols you must know

The syllabus names nine. Each has a specific shape, and using the wrong shape loses marks even when the logic is right.

1. Terminator — oval / rounded rectangle

        ╭───────────╮
        │   START   │
        ╰───────────╯

Marks the start and the end. Every flowchart has exactly one START and at least one STOP.

2. Process — rectangle

Any calculation or assignment.

        ┌───────────────┐
        │  sum ← a + b  │
        └───────────────┘

3. Input/Output — parallelogram

Reading input or writing output.

         ┌─────────────┐
        /   READ n    /
       └─────────────┘

4. Decision — diamond

A question with exactly two outgoing branches, labelled Yes/No or True/False.

              ◇
           ╱     ╲
      No ╱ a > b  ╲ Yes
        ╱           ╲

Every decision has one entry and two exits. Both must be labelled.

5. Module / subprogram call — rectangle with double side bars

        ┌──┬─────────────┬──┐
        │  │  CALL sort  │  │
        └──┴─────────────┴──┘

Indicates a named module defined elsewhere.

6. FOR loop — hexagon

The syllabus specifies a hexagon for a counted loop. It carries the initialisation, condition and increment together.

          ╱─────────────────╲
         ⟨  i ← 1 TO 50      ⟩
          ╲─────────────────╱

This is a convention worth noting — many textbooks draw a FOR loop as a decision diamond plus a process box instead. The KTU syllabus names the hexagon explicitly, so use it.

7. Flow-lines — arrows

Connect symbols and show direction. Always draw the arrowhead: an unlabelled line is ambiguous, and the marker cannot infer direction.

8. On-page connector — small circle

When a flow-line would cross the page awkwardly, break it and mark both ends with a lettered circle.

            ( A )

9. Off-page connector — pentagon / home-plate shape

Same purpose, but the flow continues on a different page.

          ┌─────────┐
          │    A    │
          └──╲───╱──┘

Rules that carry marks

• One entry, one exit per symbol, except the decision diamond which has two exits.
• Label both branches of every decision.
• Flow generally runs top to bottom, left to right. If it must go upward — as loops do — the arrow makes that explicit.
• Use the correct shape. A calculation in a parallelogram is wrong even if the formula is right.
• Connectors come in pairs. A circle labelled A must have exactly one matching A elsewhere.

The commonest mistakes

1. Rectangle used for input instead of a parallelogram
2. Decision branches unlabelled
3. Missing arrowheads
4. More than one exit from a process box
5. No STOP terminator
6. A loop drawn without a flow-line returning to the test