Explain the difference between instance variables and local variables in Ruby.

In Ruby, instance variables and local variables serve different purposes and have distinct scopes within a program.

Instance variables are variables that belong to a specific instance of a class. They are prefixed with the `@` symbol and are accessible throughout the entire object or instance of the class. Each object of a class maintains its own copy of instance variables, allowing objects to have unique data associated with them.

The key difference between instance variables and local variables is their scope. Instance variables can be accessed and modified by any method within the object or instance of a class. They persist as long as the object exists and can hold different values for each instance of the class.

On the other hand, local variables are variables that are defined within a specific scope, such as a method or a block, and are only accessible within that scope. Local variables are not associated with any particular object or instance of a class. They are created and destroyed as the program execution flow enters and exits the scope in which they are defined.

Local variables are not accessible outside their scope, which means they cannot be directly accessed by other methods or parts of the program. Each time a method or block is invoked, a new set of local variables is created, and they are discarded once the execution flow leaves the scope in which they were defined.

Another distinction between instance variables and local variables is their naming convention. Instance variables in Ruby are typically named with a single `@` symbol followed by a name (e.g., `@name`, `@age`). Local variables, on the other hand, follow standard naming conventions without any special symbols (e.g., `name`, `age`).

In summary, the main differences between instance variables and local variables in Ruby are:

1. Scope: Instance variables have object-level scope and are accessible throughout the instance of a class, while local variables have limited scope and are only accessible within the specific block or method in which they are defined.
2. Association: Instance variables are associated with specific objects or instances of a class, allowing each instance to hold unique data. Local variables are not associated with any particular object and exist only within the scope in which they are defined.
3. Lifetime: Instance variables persist as long as the object exists, retaining their values even after method invocations. Local variables are created and destroyed with each method or block invocation, and their values are not retained once the scope is exited.

Understanding the distinction between instance variables and local variables is crucial for proper data encapsulation and scoping in Ruby programs. By using instance variables, you can store and access data specific to each instance of a class, while local variables allow you to work with temporary data within specific method or block scopes.