In which cases are default data type values not stored in the heap memory area?

Default data type values (e.g., Int, Double, Bool in Swift) are usually placed on the stack rather than on the heap if they are local variables or properties of structures. The heap is used for class objects and reference types. For example, if a structure contains an Int, the value is stored inside the structure itself (on the stack or within the object), not on the heap. The heap is used when instances of classes are created using the new operator or when using reference types.