© Jennifer M. Kohnke
Infinite beatitude of existence! It is; and there is none else beside It.
—Edwin A. Abbott, Flatland (1884)
Usually, there is a one-to-many relationship between classes and instances. You can create many instances of most classes. The instances are created when they are needed and are disposed of when their usefulness ends. They come and go in a flow of memory allocations and deallocations.
But some classes should have only one instance. That instance should appear to have come into existence when the program started and should be disposed of only when the program ends. Such objects are sometimes ...