What is a runtime environment in programming?


What is a runtime environment in programming?

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Imagine when you write your code (no errors in the code itself) you put it in a box where it will run.
That box is your runtime environment.
You can add special things to the box to effect your code and if an error occurs inside that box, it’s a runtime exception

We currently use high-level programming languages. They look kinda close to plain writing, with a lot of different grammar rules and {} () ; , characters thrown in. The thing is, computers don’t actually understand this kind of code. They operate off of machine code, which is basically just sequences of binary 1s and 0s. The high-level program needs to be translated from the near english down to the machine code. This process is called compiling.

In many cases programs are compiled and then sold/distributed for use. It allows the programs to be executed much faster on the user’s computer. The problem is that different types of computers use different languages. So a program compiled to run on a system running a windows operating system will not run on a computer running MacOS.

This means that developers had to figure out a way to allow their programs to run on different platforms. One solution is to rewrite the program and compile it for every operating system and computer hardware architecture you want it to run on. That takes a lot of time and effort. It also would have to be done over and over for each program. Instead, some developers figured they would only do it once. The runtime environment is coded to run on the desired system architecture/operating system. This allows developers to write their program one time, but have it run on different systems. The runtime environment takes the program and compiles it when the user clicks on the application for the computer to run. So long as the system has the appropriate run time environment software installed, the application will run on that system regardless of operating system. Java and python are two run-time programming languages that come to my mind immediately, but I know there are a ton more.

A runtime environment is basically everything you need to actually execute a piece of code. Technically it includes the OS and hardware you are using, but when talking about runtimes the OS and hardware are usually just considered as a given.

So in the contex of say Java JRE or .NET CLR it’s the virtual machine software that loads up and executes your code. The rest of the runtime environment, OS and hardware, are usually considered as not really significant as the JRE and CLR and similar abstract away a lot of the specifics for the OS and the OS abstracts most of the specifics for the hardware.


People write the code months or years in advance. They do special processing of that human readable code to make a computer able to use it. It’s not human readable after that.

All the mistakes they make were therefore made months or years ago, and are waiting in code like seeds in the spring to sprout.

When that code is actually running, at that moment, it is in a runtime environment. All the instructions and all the places important information is kept is contained in RAM on the computer while the program runs.

Sometimes things break in code that can only be found in a runtime environment, which is why they can dump out every location in memory of that running code so they can review what it looks like versus what it should look like. This is not a quick process.

The runtime environment is code that runs as part of your application, that implements some feature of the language that you wrote your code in.

For example, the language design of C# assumes that there is a garbage collector that finds and reclaims objects that your application no longer refers to. The code that makes up that garbage collector is run as part of your application and is considered part of the runtime environment.