9.2 Algorithms: Writing Pseudo-code with Input, Process, and Output

Objective

This section focuses on writing clear and concise pseudo-code that effectively outlines the steps involved in solving a computational problem. The pseudo-code must explicitly define the input, the processing steps, and the expected output.

What is Pseudo-code?

Pseudo-code is an informal way of describing an algorithm. It uses a combination of natural language and structured elements to represent the logic of a program. It's not a programming language, but rather a blueprint for a program.

Key Components of Pseudo-code

1. Input: The data that the algorithm receives. This is typically specified at the beginning of the algorithm.
2. Process: The sequence of steps that the algorithm performs to transform the input into the desired output. This is the core of the algorithm.
3. Output: The result of the algorithm's processing. This is typically specified at the end of the algorithm.

Example: Calculating the Area of a Rectangle

Let's illustrate this with a simple example: calculating the area of a rectangle.

Step #	Description	Pseudo-code
1	Input: The length and width of the rectangle.	Get the length, $l$, and width, $w$, of the rectangle.
2	Process: Calculate the area.	Area = $l \times w$
3	Output: The calculated area.	Display the calculated area.

More Complex Example: Finding the Maximum of Three Numbers

Now, let's consider a slightly more complex example: finding the maximum of three numbers.

Step #	Description	Pseudo-code
1	Input: Three numbers, $a$, $b$, and $c$.	Get three numbers, $a$, $b$, and $c$
2	Process: Compare the numbers and find the maximum.	If $a > b$ and $a > c$ then Maximum = $a$ Else if $b > a$ and $b > c$ then Maximum = $b$ Else Maximum = $c$
3	Output: The maximum of the three numbers.	Display the maximum number.

Important Considerations

• Clarity: Use clear and unambiguous language.
• Structure: Use indentation to show the structure of the algorithm (e.g., if-then-else blocks, loops).
• Keywords: Use keywords like "Get", "Display", "If", "Else", "While", "Repeat" to make the pseudo-code easier to understand.
• Consistency: Be consistent in your notation.

Exercise

Write pseudo-code to calculate the average of two numbers.