Program Design and Development Chapter Notes | AP Computer Science Principles - Grade 9 PDF Download

Introduction

Creating a computer program involves a structured process that transforms ideas into functional software. This guide, aligned with the 2025 AP Computer Science Principles exam, explores the stages, methods, and tools involved in program development. Whether you're working on your Create Project or studying software creation, this overview will help you navigate the process.

Types of Development Processes

Program development can follow various approaches, each with its own structure and philosophy.

• Waterfall Development Model: A traditional, linear approach where each phase (e.g., planning, coding, testing) is completed before moving to the next. It’s systematic and follows a clear sequence, making it ideal for projects with well-defined requirements. 
• Agile and DevOps Methodologies: These modern methods emphasize flexibility and collaboration. Agile focuses on iterative cycles and frequent user feedback, while DevOps integrates development and operations for faster, automated delivery.
• Exploratory Development: A less structured approach where programmers experiment without rigid guidelines, often due to time constraints or undefined goals. This can lead to creative solutions but may lack predictability.

There are two general types of development processes that the College Board wants you to know about: iterative and incremental development processes

Iterative and Incremental Development

• These processes allow developers to refine programs systematically:
  • Iterative Development: Involves creating prototypes and repeatedly refining them through cycles of planning, coding, and testing. Each iteration improves the program based on feedback or testing results.
  • Incremental Development: Breaks the program into smaller, functional modules. Each module is developed and tested before being integrated into the larger system, ensuring steady progress.
• Both methods can be combined in software development. 
• Example of combining the two: You improve one section of code repeatedly (iteration), then move on to the next section, building the program piece by piece (incrementally).

 The Drawing Board: Phases of Program Development

Most development processes begin with planning, long before any code is written.  Here are the key phases:

Investigation and Reflection

• This is the planning stage to clarify the program’s goals.
• Programmers define the program’s purpose and the problem it aims to solve.
• They determine what the program needs to do and what resources it requires to function.
• Program specifications outline the program’s goals, agreed upon by programmers and clients.
• Programmers consult various sources, such as clients or team members, to ensure compatibility and clarity.
• External research may be conducted to study similar programs.
• Methods of investigation include:
  • Collecting data through surveys.
  • Conducting user testing.
  • Interviewing clients to understand their needs.
  • Observing the project in action if it has undergone prior development cycles.
• In iterative processes, this stage includes reflecting on improvements or issues, with questions becoming more specific in each cycle.

Designing Code

• The design phase plans how to achieve the program’s goals.
• Activities in this phase include:
  • Brainstorming ideas.
  • Planning and storyboarding.
  • Organizing the program into modules and functional components.
  • Creating diagrams for user interface layouts.
  • Developing a testing strategy for the program.

Program Requirements and Specifications

• Investigation helps identify program requirements, which describe how the program should work.
• Requirements include what users should be able to do and what inputs the program needs.
• Program specifications define these requirements clearly.
• Once specifications are set, programmers can start building, prototyping, and testing the program.
• Programmers document their work during development through program documentation.

Program Documentation

• Program documentation explains how parts of a program work.
• It may include details on development choices, such as why a specific coding method was used.
• Documentation can describe a code segment, event, procedure, or the entire program.
• Purposes of documentation:
  • Helps break down and explain complex programs.
  • Enables collaboration by making code understandable to others.
  • Allows others to use code without needing to understand its inner workings.
  • Ensures clarity for the original programmer and others about what the code does.

Comments

• Comments are a common form of documentation written directly in the code.
• They describe what specific parts of the code are intended to do.
• Comments are marked by symbols (e.g., #) that tell the computer to ignore them when running the program.
• Most programming languages support comments, but some do not, requiring other documentation methods.

Sourcing Your Work

Using code written by others (e.g., for your Create Project or group work) requires care:

1. Check with your teacher to ensure the code is allowed for class use.
2. Verify usage permissions, as code may be licensed with specific restrictions.
3. Cite your sources in the documentation, noting the original author and code origin.

Citation formats vary, but online guides can help. Always acknowledge external contributions to maintain academic integrity.

Key Terms

• Agile Development Methodologies: Flexible, iterative approaches prioritizing adaptability, collaboration, and frequent feedback to deliver software in short cycles.
• Comments: Non-executable notes in code that explain its purpose or functionality.
• DevOps Development Methodologies: Combines development and operations to enhance collaboration, automation, and efficient software delivery.
• Incremental Development Process: Adds features gradually in small, functional modules, enabling early delivery of working components.
• Iterative Development Process: Divides development into cycles of planning, coding, and testing, allowing continuous refinement.
• Program Requirements: Specific features and functionalities a program must have to meet user needs.
• Program Specifications: Detailed descriptions of a program’s functionality and behavior, guiding its design.
• Program Documentation: Written materials explaining how to use and maintain a program, including instructions and diagrams.
• Waterfall Development Model: A linear, sequential approach where each development phase is completed before the next begins.