How do you name a class and the name should stand for: iPhoneX, iOS ? Do you name them IPhoneX and IOS? or how do you name a class if the name in real world starts with lowercase letter?

Always, without exception, start class names with an uppercase letter.

Why so?

Because of Coding Convention

Why than is not restricted by compiler?

Because we rely on capitalization to tell us whether something is a class or a variable/function.

Kotlin is not so strict about it, you can use own, but official convention requires that

Because it's not helpful to enforce such a thing.

it is helpful, compiler can be much simpler

simpler?

yeap, when you parse a string, if it starts with capital you already know that it must be a class

I don’t think so, because other identifiers can use capital letters too, for example objects, constants etc

hm... word

class

is quite a giveaway, even before you notice a capital letter 🙂

but in function body you don't have

class

and in places other than class declaration Andrey's comment applies, you can't rely on capitalization there.

we can inforce variables and function to start with lowercase

See comment from Dmitry Jemerov about strict coding convention https://github.com/yole/kotlin-style-guide/issues/14#issuecomment-222932510

so, everyone agree to start class with capital, but do not enforce that in compiler, okay

@rrader Also, I’m not a professional in compilers, but I’m very sceptical that naming convention could some how help to compiler

well,

class

somehow helps in parsing, in same way this will help

class is a keyword that cannot be used anywhere except class creation, lower or capital letter can be used everywhere, including keywords