Form 3 ICT

Flowcharts: Making Decisions

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Your report book says Pass or Fail next to each subject. A computer printed it, but nobody typed those words for each student. How did the computer decide which word to print?

In this post:

  • What selection is, and how the decision symbol works
  • A pass/fail flowchart you can run
  • A grades flowchart with several decisions
  • Turning game rules into decisions, a tracing activity and a quiz

Selection: choosing a path

In a sequence, every step happens. With selection, the algorithm asks a question and chooses which steps to do next, depending on the answer. In a flowchart, the question goes in a decision diamond. Two arrows come out: one labelled Yes (the condition is true) and one labelled No (it is false). Afterwards, the two paths usually join up again.

Conditions often compare values using these signs, called relational operators:

SignMeaningExample (mark = 50)
=is equal tomark = 50 → Yes
<>is not equal tomark <> 50 → No
>is greater thanmark > 50 → No
<is less thanmark < 50 → No
>=is greater than or equal tomark >= 50 → Yes
<=is less than or equal tomark <= 50 → Yes

Example 1: pass or fail

Try it: run the pass/fail flowchart

Type a mark, then step through. Try 72, then 35, then exactly 50. Which path does each mark take?

Input (mark):

StartInput markmark >= 50?YesNoOutput “Pass”Output “Fail”Stop

Variables

Output

What just happened

    Why >= and not >? If the pass mark is 50, a student who scores exactly 50 has passed. mark > 50 would wrongly print “Fail” for 50. Always test the boundary value.

    Example 2: grades, with several decisions

    Here, the school gives an A for 75 and over, a B for 60 to 74, a C for 50 to 59 and a D below 50. One decision is not enough, so the flowchart asks up to three questions, one after another. As soon as one answer is Yes, it outputs the grade and goes to Stop.

    Try it: run the grades flowchart

    Try marks that give each grade, including the boundary marks 75, 60 and 50. Count how many decisions each mark goes through.

    Input (mark):

    StartInput markmark >= 75?YesNomark >= 60?YesNomark >= 50?YesNoOutput “A”Output “B”Output “C”Output “D”Stop

    Variables

    Output

    What just happened

      A Flowgorithm flowchart: Main, declare a real variable called value, output a prompt, input value, a decision value > 0, with two outputs saying whether the number is positive or not, then End.
      A selection flowchart made in Flowgorithm. It inputs a number, asks “value > 0?” and outputs whether the number is positive. The extra rectangle near the top declares (creates) the variable, which Flowgorithm needs before you use it. In Flowgorithm, the start is called Main.

      Image source: File:Flowgorithm Conditions.svg (Wikimedia Commons)

      Watch: if-else decisions in a flowchart

      This video shows how to draw a decision with different steps for when the condition is met and when it is not, called an if-else.

      Video: Making If-Else Style Decisions in a Flowchart – Access 2 Learn – https://www.youtube.com/watch?v=xC8h8ALwPvs

      Activity: game rules as decisions

      Remember the Snakes and Ladders algorithm? Its rules are decisions. “If the counter lands at the foot of a ladder, climb up” becomes a diamond asking “On a ladder?”. Yes leads to a process, “Move to the top of the ladder”. No skips it. Draw the flowchart for one turn: roll the die, move, check for a ladder, check for a snake, and check for square 30.

      Activity: predict the path

      Try it: what is the output?

      Use the grades flowchart (A 75+, B 60–74, C 50–59, D below 50). Type just the letter.

      1. mark = 90

      2. mark = 75

      3. mark = 74

      4. mark = 50

      5. mark = 49

      Self-check quiz

      Click the best answer. You get feedback straight away; only your first click counts towards your score.

      1. Which symbol is used for selection in a flowchart?

      2. How many labelled arrows leave a decision symbol?

      3. The pass mark is 50. Which condition gives the right answer for a mark of exactly 50?

      4. In the pass/fail flowchart, what is output for a mark of 49?

      5. What does <> mean?

      6. Why does the grades flowchart need more than one decision?

      Related posts on islandclass.org

      For later, in Forms 4–5 (CSEC IT): these go deeper and are for when you reach CSEC Information Technology.

      Next: Flowcharts: Repeating Steps with Loops

      Syllabus link: Forms 1–3 ICT curriculum, Module 5, Objective 5.11 – use flowchart symbols appropriately to represent an algorithm using a selection construct.

      Attributions to media used in this post:

      Updates

      2026/10/21

      - Fixed the activity code so its buttons keep working.

      © 2026 Vedesh Kungebeharry. All rights reserved.

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