Declaration, initialization, instantiation

Previous: Variable assignment and initialization in C++

Declaration: Telling the compiler that a variable or object exists, specifying its type. No memory for the actual value is necessarily allocated (depends on context). Example:

• int x;
• Foo* p;

Initialization: Assigning an initial value to a variable or object. Happens after declaration or at the same time. Example:

• int x = 5;
• Foo obj(10);

Instantiation: Creating an instance of a class (an actual object). Involves memory allocation for the object. Example:

• Foo obj; (stack allocation)
• Foo* p = new Foo(); (heap allocation)