Structured programming notes

1. What is a Flowchart?

A flowchart is a diagrammatic representation of an algorithm or process.

• It uses symbols to represent different steps.

• Helps visualize the flow of control, especially in structured programming.

Common symbols:

2. Examples of Flowchart Descriptions

Example 1: Find the largest of two numbers

Description: The program reads two numbers and prints the largest one.

Flowchart Steps:

1. Start (Oval)

2. Input number A and number B (Parallelogram)

3. Decision: Is A > B? (Diamond)

   • Yes: Print A (Rectangle)

   • No: Print B (Rectangle)

4. End (Oval)

Explanation:

• The diamond represents selection, choosing which number to print.

• The flowchart clearly shows the decision and the flow to the end.

Example 2: Print even numbers from 1 to 5

Description: The program prints only even numbers from 1 to 5 using a loop.

Flowchart Steps:

1. Start (Oval)

2. Set i = 1 (Rectangle)

3. Decision: Is i <= 5? (Diamond)

   • No: Go to End

   • Yes: Continue

4. Decision: Is i MOD 2 = 0? (Diamond)

   • Yes: Print i (Parallelogram)

   • No: Skip printing

5. Increment i = i + 1 (Rectangle)

6. Go back to Step 3 (loop)

7. End (Oval)

Explanation:

• Combines iteration (loop from 1 to 5) and selection (print only if even).

• Flowcharts make loops and decisions visually clear.

Example 3: Sum positive numbers until zero is entered

Description: Keep reading numbers, sum the positive ones, and stop when 0 is entered.

Flowchart Steps:

1. Start (Oval)

2. Set sum = 0 (Rectangle)

3. Input number (Parallelogram)

4. Decision: Is number = 0? (Diamond)

   • Yes: Go to Step 6 (End)

   • No: Continue

5. Decision: Is number > 0? (Diamond)

   • Yes: Add number to sum (Rectangle)

   • No: Skip addition

6. Go back to Step 3 (loop)

7. Output sum (Parallelogram)

8. End (Oval)

Explanation:

• Iteration: Loop continues until 0 is entered.

• Selection: Only positive numbers are added.

• Flowchart shows decision-making and repetition clearly.