SWIFT – If you are developing an app for Apple Products then swift is the compile programming language. It is produced by apple in 2014, swift is faster than objective-C, it was built with high performance in mind and the safeguards prevent error and improve readability.
C++ – C++ is an extension of C language, if you want build windows and android applications then C++ simplistic programming language, it dominated the programming world before the smart phones trend, C++ is adaptable for various platforms.
JAVA – This is a popular programming language generally used for android app development, this object-oriented programming language is fast, reliable and secure, java can run in window browser or virtual machine. It will be a plus point to learn java for an app developer.
HTML5 – HTML5 is ideal for developing the web-fronted applications for mobile, it is supported by all trendy browsers and it also supports audio and video controls, the languages are also improved in this programming language so it is an advantage to build an app with the latest version of HTML.