> iPhone calculator is a skeuo calculator because it has the same layout and limitations of a physical calculator.
In that case you can also consider the iPhone "dialer" to be skeuomorphic, as it has the same layout as the old physical buttons. The digital keyboard is also using the same layout as a physical keyboard.
One could argue that on a touch screen, the buttons are there because it is the most efficient layout and not because it looks like a physical calculator. In that case, it is not skeuomorphic.
The iPhone dialer definitely is. I'm not saying that's bad or anything, some things are better being skeuomorphic if it helps users understand the interface. It's just the actual user interface design discussion gets drowned out by how honestly for lack of a better word embarrassing most digital design discourse is in general it's been changed into more of an art direction debate than a UI design one.
>One could argue that on a touch screen, the buttons are there because it is the most efficient layout and not because it looks like a physical calculator. In that case, it is not skeuomorphic.
It definitely is designed to be a physical calculator though to the extent it is an actual copy of a famous one [1], and has all the limitations of a physical calculator even mincing the memory limitations of a physical calculator.
Your source image is over a decade out of date. The current calculator has no simulated physical button contour, no simulated plastic face plate, no simulated LCD layout, or any other attempt to be mimic the materials and construction of a physical object. It uses a layout similar to all other calculators because there's no reason to make people change their mental model of entering numbers for computation. Same with the current iPhone dialer. It makes no attempt to appear like a physical object rather than an abstracted method of inputting data. Skeuomorphic doesn't mean "being like something else that exists in some way." The first paragraph from Wikipedia:
A skeuomorph (also spelled skiamorph, /ˈskjuːəˌmɔːrf, ˈskjuːoʊ-/)[1][2] is a derivative object that retains ornamental design cues (attributes) from structures that were necessary in the original.[3] Skeuomorphs are typically used to make something new feel familiar in an effort to speed understanding and acclimation. They employ elements that, while essential to the original object, serve no pragmatic purpose in the new system. Examples include pottery embellished with imitation rivets reminiscent of similar pots made of metal[4] and a software calendar that imitates the appearance of binding on a paper desk calendar.[5]
So a software calendar using the same layout as a paper calendar doesn't mean it's skeuomorphic. It means it's a calendar. If you had a totally unique calendar interface model but added a sewn leather binding graphic along the top, it would be skeuomorphic.
The key to skeuomorphism is that it's based on unnecessary ornamentation, like giving a button on a computer a 3D look, or having a display in an app have a fake glass sheen.
For example
iPhone calculator is a skeuo calculator because it has the same layout and limitations of a physical calculator.
Soulver is a non-skeuo calculator because it is built around the benefits of a computer and ignores the history of a calculator.