Event Driven Programming Principles

Event Driven Programming

• Event-driven programming is a programming paradigm where the flow of execution is governed by events, like user interactions or system-generated events.
• Events are handled by event handlers or event callbacks, which are functions designed to respond to specific events.
• This paradigm is prevalent in modern software engineering, particularly in graphical user interfaces (GUIs) and applications that react to user input.
• Event-driven programming relies on events as the foundation for software development.

Principles of Event-Driven Programming

• Event handlers: Functions that handle events; these can be blocking (halt execution until the event is processed) or non-blocking (continue execution while handling the event).
• Event binding: A mechanism connecting registered event handlers to specific events.
• Main loop: Continuously polls for new events and calls the appropriate event handler(s) when a registered event is received.

Features of Event-Driven Programs

• Service-oriented: Programs designed to provide services.
• Time-driven: Code that executes based on a time trigger (e.g., running weekly or upon program launch).
• Event handlers: Functions triggered upon the occurrence of a specific event.
• Trigger functions: Determine the code that runs when a specific event occurs, selecting the appropriate event handlers for the event.

Events and Triggers

• Events are triggered by user interactions with objects, such as clicking a button or typing on the keyboard, or by system events.
• Events can involve mouse actions (clicks, movement, scrolling), keyboard inputs, or user interface elements.

Pre-defined Functions, Variables, and Parameter Passing

• Pre-defined Functions: Functions built into the programming language (e.g., Main() in C#) provide basic functionalities.
• Local Variables: Variables declared within a method, accessible only within that method.
• Global Variables: Variables accessible from any part of the program.
• Parameter Passing: Allows values to be passed to functions, enabling various tasks, including setting alarms or finding specific characters.
• Four parameter passing methods in C#:
  • Value: Creates a duplicate copy of the variable, so changes in the called function do not impact the original variable.
  • Ref (reference): Passes the address of the variable, allowing changes in the called function to affect the original variable.
  • Out (reference): Similar to ref, but the variable doesn't need to be initialized before being passed.
  • Params (parameter arrays): Used for passing a variable number of arguments as an array to a function.

Modularity

• Modularity: Breaking down a program into independent modules, each responsible for specific tasks. This simplifies program development and maintenance.
• Modules: Units of code with:
  • Interfaces: Define the module's public components.
  • Encapsulation: Hide internal implementation details.
• Modules depend on interfaces, promoting independence and maintainability.

Procedures and Programming Libraries

• Procedures: Small programs (sub-programs) used to avoid code repetition and carry out specific tasks.
• Programming Libraries: Collections of pre-compiled routines, data files, scripts, templates, and other resources. These libraries simplify development by providing reusable components.

Advantages of Event-driven Programming

• Ease of programming and development: Event-driven programming is often more intuitive and visually driven, making it easier to develop user interfaces.

Examples of Event-driven Programming Languages

• Visual Basic
• Java
• C#

This quiz covers the fundamentals of event-driven programming, a key paradigm in modern software development. Participants will explore concepts such as event handlers, event binding, and the main loop mechanism that drives responsive applications. Test your understanding of how events govern software execution and user interactions.