Kotlin Facts For Kids

Kotlin is a modern computer language people use to write apps for phones, websites, and servers. A computer language tells a machine what to do. Kotlin is called "statically typed," which means the computer checks the kind of each piece of information before the program runs so some mistakes are found early. It also has "type inference," which lets the writer skip naming types when the tool can figure them out.

Kotlin mainly runs on the JVM, the same place many Java programs run, so it can use lots of existing Java code. It can also turn into JavaScript for web pages or into native code for other devices.

A team at the software company JetBrains started the project. They named it after Kotlin Island near Saint Petersburg, following a similar idea to the language Java, which is named after an island too. The first code was added on 8 November 2010, and JetBrains first spoke about Project Kotlin in July 2011 because they wanted a language that compiled faster than some others.

Kotlin’s first official, stable version, called 1.0, was released on 15 February 2016. JetBrains pays for much of the work, and the Kotlin Foundation helps protect the name so many people can use the language safely.

Kotlin was designed to be an industrial-strength, object-oriented language. That means it helps programmers group data and the actions that work on it into tidy pieces called objects. The designers wanted a language that felt nicer and safer to use than some older languages, but that would still work smoothly with Java programs and libraries.

Being "interoperable" means Kotlin and Java can call each other’s code as if they were friends sharing toys. Small conveniences also help writers: for example, you do not always need a semicolon at the end of a line because the compiler usually understands where a statement stops.

A Kotlin program often starts with a function named main that can receive words from the command line in an array called args. Kotlin keeps apart types that can hold no value from those that must have a value. A nullable type has a '?' after it, and Kotlin gives tools like the safe-navigation operator and the Elvis operator to check for missing values and pick sensible defaults.

Kotlin uses short, handy functions called lambdas, written with braces {} and parameters before an arrow ->. It also has 'data classes' that store information and auto-make helpful methods like equals and toString. You can add 'extension functions' to existing classes without changing them, and there are five scope helpers—let, run, with, apply, also—that make working inside an object easier.

Kotlin Multiplatform means you can write one set of instructions (a codebase) and use it on many kinds of devices: phones, tablets, desktop computers, and websites. Because the same code can run in different places, programmers do not have to rewrite everything for each device. They write shared parts—like the rules of a game or the math in an app—and then add small pieces that fit each device’s screen and buttons.

This approach saves time and helps apps work the same way everywhere. Tools help turn the shared code into versions that work on Windows, Linux, Android, iOS, or the web, while still letting developers tweak the parts that need to look or feel different.

Kotlin became one of the main languages for building Android apps after Google announced support in 2017. By 2020 it was used a lot on Android—Google said about 70% of the top 1,000 apps used Kotlin, and many Google apps, like Maps and Drive, use it too. Lots of apps were being moved from older code to Kotlin, so some apps use both Kotlin and Java while they change over.

Programmers like Kotlin because it helps prevent a common error where the program looks for something that isn’t there (often called a "null" mistake) and because it can make code shorter and easier to read. That helps teams build better apps faster, so many of the games and tools kids use on phones may be made with Kotlin.