There are tons of applications on Desktop platforms that need specific skills sets such as: photoshop for working with images, socket programming for writing something like dropbox, engineering if you want to build a compiler.

When it comes to languages for desktop applicalations the choice is tough between C++, Java, or C#. Take a look at the samples below to simplify choosing:

• Oracle: Java
• Linux : C++
• MacOS : C++

If you want to make Android Apps, you should choose between Java and Kotlin:

To make the correct choice, we should look behind the scenes.

To be a competent developer in the market, you have to support previously implemented Apps in Java. 

To be an iOS developer, you need to go with Swift. To be a really confident developer, it is suggested to master Objective-C to support Apps (tons of Apps) already written in Objective-C.

To successfully prepare for coding interviews you should be confident in the following areas:

1. Algorithms & Data Structures 
2. Computer Organization & Operating Systems
3. Coding
4. System Design