How to write cross-platform software?

Question

Mobile development

Good afternoon.
There was a need to write a program for a PC, and later for smartphones.
The program hangs in the tray and provides the user with the ability to view some objects from a specific website. Send messages through this program to the site and read the responses.
The issue is choosing a programming language. At the same time, not only for writing a program, but also for further use, job search.
Those. the language should be quite popular and in demand in the labor market. (Java? C++? C#? Other?)
Please write your thoughts on this. Only with your justification why you recommend this particular programming language.

Answer 1

Well, I would choose: html, css, js + nodejs + node-webkit + phonegap.
Although C# for example is also suitable.
In the first case, the job market is very large, try everything, decide what will be more interesting for you.

Answer 2

The toaster is just full of such questions. Just look here for answers first.
Cross-platform languages ​​are java, javascript, c++ and others but not C#

Answer 3

Judging by your description, I think that Java would be a good fit for you, because:
       - it is cross-platform and was created just for use on a variety of devices. You can first write your application to run on computers, and then modify it to work on tablets and mobile devices running the Android operating system;
       - the language is very popular and now most of the requested vacancies with decent salaries in the IT market are Java developers;
       - a lot of materials and courses for self-study of this language (I have already listed the Selection for beginners "Javists" );
       - very simple and understandable for learning, both for beginners and those who decide to deepen their knowledge;
       - there are a large number of convenient IDEs for developing in this language.
Thank you for your attention and success in development!