What is the purpose of a constructor in programming?

The purpose of a constructor in programming is to set initial values for an object's attributes. When an object of a class is created, the constructor is invoked automatically, allowing the programmer to initialize instance variables or perform any setup needed for the object. This is crucial because it ensures that the object starts in a valid state before any methods are called or operations are performed on it. By providing initial values, constructors help maintain the integrity of the object and dictate its initial behavior, which can affect how the object's methods interact and function throughout its lifetime.

The other options do not correctly define the role of a constructor. Defining methods is a function of the class itself rather than the constructor specifically; compiling code is a separate process that transforms source code into executable files; and implementing data security is unrelated to the core purpose of a constructor. Thus, the correct answer highlights the primary responsibility of a constructor in object-oriented programming.