What to study for writing your own cross-platform application?

Question

Programming

Experience in programming: Pascal in school. I know HTML, CSS, JS basics. I want to write a simple application (let it be To-Do) that can be run on Windows, Mac, iOS, Linux.
This is real? Or is it better to concentrate on one platform first? What do you need to learn for this?

Answer 1

The basic principles of programming are platform or language independent. You should study what you like. There are enough cross-platform APs. For example C# - for it there is Xamarin.

Answer 2

>> Паскаль в школе.
Тогда тебе понравится FreePascal/Lazarus.
C другой стороны нужно понимать, что истинные кроссплатформенные приложения могут быть только web-приложения. Можно использовать JAVA.

Answer 3

Stdlib, boost, Qt

Answer 4

This is a problem for logic (arithmetic), and not for programming.
If 2 amoebas are planted, then this is the same as one amoeba in a second.
Those. you saved one second, the answer is 59.
And it doesn’t seem to converge because i must start from 1 and not from 0.