What is Adobe AIR?

I don't believe that Acrobat Reader is installing it anymore, but Adobe AIR
is a runtime support library that is used by other programs. (It's often
referred to as a "common" runtime support library because its use is common to a
number of other programs.)

If that definition sounds familiar, that's because it is. Adobe AIR is by no
means the first common runtime library. In fact, you probably already have
several.

I'll discuss what's going on.

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Runtime support libraries

Common libraries typically try to address two specific problems that programmers face:

• They don't want to have to write the same software over and over again.

• They want their software to run on as many different machines as possible.

Let's first look at writing that same software over and over.

Not reinventing the wheel

To use an extremely simple example, imagine software that takes two strings and joins them together into a single string. The software might take the strings "run" and "time" and create the string "runtime" from them. This operation is referred to as concatenation and it is an extremely common operation that almost all software needs to do at one time or another.

One approach is to have each program have its own instructions for concatenating two strings. That means that every time that a program is written, a programmer has to find or write the software, and then, hopefully test it as well.

Another approach is to provide that functionality once in such a way that it can be used by many programs. These programs simply need to know where to look and how to find this functionality; once they do, they can simply use it without having to reinvent the wheel.

Windows does indeed have a library function to concatenate two strings.

Runtime libraries like Adobe AIR are in part just collections of functionality made available to other programs. Typically, the functionality provided is significantly more complex than concatenating two strings; however, it's often functionality that is also extremely common or useful for many programs to have.

Running on multiple platforms

Libraries of functionality can be written in such a way that they can be used on different types of computers. What that typically means is the applications that use these libraries are written in a way that doesn't rely on any specific machines characteristics. Instead, they access the machine only through the library.

Moving to a different type of computer then means that the application itself need not necessarily be rewritten. Instead, only the library through which it accesses the system is rewritten for each new type of computer. Once that library becomes available, then all of the programs written using that library will in theory work on all of the platforms on which the library is available.

In practice, this isn't 100% true, but it can drastically reduce the amount of work necessary to alter an application running on one platform to run on another.

The downside to the multi-platform support that is provided by the library is typically one of speed and sometimes reduced functionality. Writing an application in a platform-independent manner requires that it not take advantage of all of the characteristics or features that might be unique to a specific platform.

Adobe AIR

Adobe AIR is Adobe's entry into the common runtime library market. Several popular programs that are currently available rely on Adobe AIR to provide the base functionality. Examples include programs, like TweetDeck, HBO Go, and others.

Adobe AIR appears to be focused on being a cross-platform development library for developers who are attempting to develop mobile applications; as you can see, however, the Adobe AIR runtime is available for desktop operating systems as well.

Quoting the Adobe site:

The Adobe® AIR® 2.7 runtime enables developers to use HTML, JavaScript, Adobe Flash® and Flex technologies, and ActionScript® to build web applications that run as standalone client applications without the constraints of a browser. Adobe AIR, a key component of the Adobe Flash Platform, unleashes the creativity of designers and developers by providing a consistent and flexible development environment for the delivery of applications across devices and platforms. Support for Android™, BlackBerry® Tablet OS, and iOS mobile operating systems and televisions is now available.

Other examples

As I said, Adobe AIR is not the only common runtime. In fact, you probably already have several on your machine.

Java, originally from Sun Microsystems, now owned by Oracle, is a programming language that is machine independent and supported by the Java runtime or "virtual machine". Many web and standalone applications use Java as their underlying technology. (Java is not to be confused with JavaScript. They are two different things with confusingly similar names.)

The Microsoft .net framework is a similar runtime library intended to make writing Windows applications easier using Microsoft's programming tools. Not only do you probably have the .net runtime on your system, but it's not uncommon to have several versions.

Programs written in programming languages, such as C, C++, or Visual Basic, often also rely on common libraries. The Visual Basic runtime has been around for many years and a library of common functionality for C and C++ programs is usually present on most systems.

Where do they come from?

Common runtime libraries typically come from either of two places:

• They're pre-installed on your system. Recent versions of Windows, for example, include versions of the .net runtime and the C runtime. The only time that you would need to download these would be if a new version were to be made available. In most cases, this is handled transparently through Windows update.

• An application that you're installing requires a particular common runtime and as a result, it either installs it for you or instructs you to install it first.

How do we get rid of them?

In general, you probably shouldn't.

Common runtimes are usually on your system for a reason and that reason is that some other software on your machine requires them.

If you're very concerned, you can backup your system first and then attempt to uninstall a common runtime using the Control Panel if it's listed there. Chances are that you may find that some program that you use will no longer work.

The good news is that, other than taking up some disk space, common runtime libraries are typically benign if not used.