Programming is about much, much more than just learning as many languages as possible. You need to understand how to execute each one well to become a great IT professional. However, each language is an additional tool you can use to create better programs and websites, so it is definitely worth looking into which ones would be of use.
Of course, there is no one-size-fits-all answer to "what programming language should I develop?" as it very much depends on what you're aiming to achieve. What are you planning to develop? For what platform? To what end?
Whatever your overall objectives are, there should be at least one language you will benefit from learning. Here are some of the most useful for each of the many tasks developers might undertake:
App development (iOS): Swift
UserSnap's Kyle Prinsloo is about as clear as you can get on this issue: "If you’d like to become an iOS app developer, learn Swift." It is Apple's own programming language, the most recent incarnation of which - Swift 3 - is used on macOS, iOS, watchOS and tvOS. There's even an official app - Swift Playgrounds - for iPad that can be used to learn the basics.
App development (Android): Java
If you don't already know Java, then now would be the best time to learn. A survey of job postings found that positions that mentioned knowledge of Java increased by almost 30,000 between 2016 and 2017, showing how in-demand this programming language is.
While it is a good language to know for a variety of reasons - Fortune 500 companies overwhelmingly use it for server-side development - we've put it in here as something to learn specifically for Android app development. All native apps on this OS are built in Java, making it an essential for anyone interested in moving into this area.
App development (web): Rust
StackOverflow's Developer Survey 2017 found that Rust is the most loved programming language out there for the second year in a row, which is extremely impressive. Although the language is fairly general, programmers have found that it is well-suited to creating secure apps for web.
This is epitomized by the fact it's used for Dropbox, which needs to be as secure as possible by nature. Rust is also surprisingly reliable and can be used to create apps that run very quickly, thanks to its ability to make the most of multi-core processors.
Business programming: Ruby on Rails
Ruby is a dynamic language that has been the tool of choice for many businesses since last year. Its new framework, Ruby on Rails, is an improvement according to TechWorm. The site said the language is more agile, with a modular approach for developing applications, all of which makes it great for rapid web development.
AppDynamics says languages like Ruby on Rails are "the perfect choice for business applications when time to market is critical", which explains why it has become so popular with startups and large firms alike.
Preparation for the future: Python
If you're looking to get ahead of current trends and learn a language that looks like it's going to be huge - rather than one that already is - then you can't do much better than Python. More and more developers are using it, as well as major sites such as Instagram and YouTube.
Worldwide, it is the fastest-growing language in terms of popularity according to the PYPL PopularitY of Programming Language Index, with its market share increasing by 7.7 per cent. It's also the current 'starter language' for many universities, so now is a great time to get on board with it before it becomes something everyone can do.