11.3 Structured Programming: Using Procedures

In structured programming, algorithms are broken down into smaller, manageable units. Procedures (also known as subroutines or functions) are a fundamental tool for achieving this. They allow us to encapsulate a sequence of instructions into a named block, which can then be called and reused multiple times within the main algorithm. This approach significantly improves code organization, readability, and maintainability.

Why Use Procedures?

There are several key reasons why using procedures is appropriate in algorithm construction:

• Modularity: Procedures divide a complex problem into smaller, self-contained parts. This makes the overall algorithm easier to understand and debug.
• Reusability: Once a procedure is defined, it can be called from different parts of the algorithm or even from other programs, avoiding code duplication.
• Readability: Using meaningful names for procedures makes the algorithm's logic clearer and easier to follow.
• Maintainability: If a part of the algorithm needs to be changed, it can be done within the procedure without affecting the rest of the code.

When to Use Procedures in an Algorithm

Procedures are particularly beneficial in the following situations:

1. Repeating Tasks: If a sequence of instructions needs to be executed multiple times, a procedure can be created to encapsulate that sequence. For example, calculating the area of multiple shapes can be handled by a procedure.
2. Complex Calculations: When a set of calculations is involved, a procedure can perform these calculations and return a result. This simplifies the main algorithm and makes it easier to read.
3. Input/Output Operations: Procedures can be used to handle input from the user or output to the screen, separating these tasks from the core logic of the algorithm.
4. Data Manipulation: Procedures can be designed to perform specific operations on data, such as sorting, searching, or validation.

Example: Calculating the Area of Shapes

Consider an algorithm that needs to calculate the area of various shapes (circles, rectangles, triangles). Instead of repeating the area calculation code for each shape, we can define a procedure called calculate_area.

Step	Description
1	Define a procedure calculate_area that takes the shape type and necessary dimensions as input.
2	Inside the procedure, use conditional statements (e.g., if statements) to determine the appropriate area formula based on the shape type.
3	Perform the area calculation using the relevant formula.
4	Return the calculated area.
5	In the main algorithm, call the calculate_area procedure for each shape, passing the appropriate parameters.

This approach makes the algorithm more organized and easier to modify if a new shape needs to be added.

In Summary

Procedures are a crucial element of structured programming. They promote modularity, reusability, and readability, making algorithms easier to design, understand, and maintain. They are most appropriate when a sequence of instructions needs to be performed repeatedly, when complex calculations are involved, or when specific data manipulations are required.