Cross-platform software facts for kids

Kids Encyclopedia Facts

"Cross-platform" redirects here. For the railway station interchange, see cross-platform interchange. For the video game term, see cross-platform play.

"Multi-platform" redirects here. For the mode of storytelling in television, see multi-platform television.

In computing, cross-platform software is computer software that works on many different types of computer systems. It's also called multi-platform software. This means a single program can run on various devices, like your computer, phone, or tablet.

For example, a cross-platform app might work on Linux, macOS (Apple computers), and Microsoft Windows (most PCs). Some software needs a special version for each system. But other software can run anywhere without much fuss. This is often because it's written in a special language that can be understood by many systems. Some popular tools for making cross-platform apps include Flutter, React Native, and Qt.

What is a Platform?
- Hardware Platforms
- Software Platforms
  - Java Platform
How Cross-Platform Software is Made
Cross-Platform Programming
- Approaches to Cross-Platform Programming
- Toolkits and Environments
Challenges
See also

What is a Platform?

When we talk about a "platform," we mean the type of computer system a program runs on. This can be the kind of processor (the computer's brain), the operating system (like Windows or Android), or a mix of both.

For example, Android is a common platform for smartphones. It usually runs on ARM processors. Other well-known platforms are Linux, macOS, and Windows. Programs are made to use the specific features of a platform.

Hardware Platforms

A hardware platform refers to the type of processor inside a device. Think of it like the engine in a car. For example, ARM and x86 are two main types of processors. Different operating systems can run on these different hardware types.

Most smartphones and tablets use ARM processors. They often run Android or iOS (for Apple devices).

Software Platforms

A software platform is usually an operating system (OS) or a special environment where programs run. Sometimes, it's a mix of both. For example, Java uses a special "virtual machine" (VM) that lets its programs run on many different OSs and hardware types.

Some common software platforms are:

Android
ChromeOS
iOS and iPadOS (for Apple mobile devices)
Java
Linux
macOS
Microsoft Windows
Web browsers (like Chrome or Firefox) – these run web apps written in languages like JavaScript.
PlayStation 4, PlayStation 3, Xbox (game consoles)

Java Platform

The Java language is special because its programs are designed to run on a Java virtual machine (JVM). You can think of the JVM as a "software CPU." This means that if a computer has a JVM installed, it can run any Java program, no matter what kind of computer it is. This is the "write once, run anywhere" idea.

Java programs can use services from the computer's operating system, like saving files or connecting to the internet. The JVM helps the Java program talk to the OS. Java software works on Windows, macOS, Linux, and many mobile devices.

How Cross-Platform Software is Made

For software to be called cross-platform, it needs to work on more than one type of computer system or operating system. Making such software can be tricky because different operating systems have different ways for programs to talk to them (called application programming interfaces or APIs).

Just because a program is written in a popular language like C or C++ doesn't mean it will automatically run on every operating system. It might even need changes for different versions of the same OS.

Web Applications

Web applications are usually cross-platform because they can be used from almost any web browser. The web browser acts as the platform. Web applications often use a client–server model. This means some work is done on your device (the client), and some is done on a powerful computer far away (the server).

Simple web apps do most of their work on the server and send the results to your browser. This was common when the internet was new. Today, these are still used when being simple and working everywhere is more important than having lots of fancy features.

More advanced web apps, like Gmail or Google Maps, use special features found in newer web browsers. These features include Ajax and JavaScript, which help make the apps feel faster and more interactive.

Design Strategies

Because developers want apps to work everywhere but also have cool features, they use different design methods.

Graceful Degradation: This means the app tries to give everyone the same features. But if your browser is old or simple, it might offer fewer features. For example, Gmail might switch to a "basic mode" if your browser can't handle all the fancy stuff.
Multiple Codebases: Sometimes, developers create completely separate versions of the software for each platform. This takes more work to keep updated, but it can be good if each platform needs a lot of unique code.
Single Codebase: This is when developers use one main set of code that can be changed slightly to work on different platforms. They might use "conditional compilation," where certain parts of the code are only used for specific systems.
Responsive Web Design: This is a way of designing websites so they look good and are easy to use on any device, from a small phone to a big desktop monitor. It uses very little platform-specific code.

Testing Web Apps

Cross-platform apps need a lot more testing. Developers have to check if the app works correctly on many different browsers and devices. Sometimes, special tools are used to help test the app across all these different systems.

Traditional Applications

Even though web apps are popular, many people still use traditional software that you install on your computer. The difference between web and traditional apps can sometimes be blurry, but it's still a useful way to think about them.

Binary Software

Traditional software is often given to you as "binary files," which are ready-to-run programs. These programs usually only work on the specific platform they were made for. So, a cross-platform program like Firefox (a web browser) has separate versions for Windows, macOS, and Linux. Even though they come from mostly the same main code, you download the specific version for your computer.

Sometimes, a special file called a "fat binary" combines code for several platforms into one file. This is rare.

Another way to make apps work on different systems is "cross-platform virtualization." This lets programs made for one system run on another without changing the original code. For example, Apple's Rosetta allowed older Mac apps to run on newer Macs with different processors.

An example of cross-platform binary software is LibreOffice. This office suite works on Windows, macOS, Linux, Android, iOS, and many other systems, and on different types of processors.

Scripts and Interpreted Languages

A "script" is like a set of instructions for a computer. A script can be cross-platform if the program that reads and runs it (called an "interpreter") is available on many systems. For example, a script written in Python for a Linux computer will likely run on Windows too, because Python interpreters are available for both.

Unlike binary files, the same script file can often be used on any computer that has the right interpreter. This is because scripts are usually simple text files.

Some popular cross-platform scripting languages are:

Python: Easy to write and good for quick app development.
PHP: Mostly used for making web applications.
Ruby: An easy-to-read language, also used for web apps with Ruby on Rails.
Bash: A common command-line tool on Linux and other similar systems.

Video Games

The term "cross-platform" also applies to video games released on many different video game consoles. Famous examples include Minecraft, FIFA series, and Tomb Raider: Legend. These games are available on systems like Wii, PlayStation 3, Xbox 360, personal computers, and mobile devices.

Sometimes, it's harder to make a game for certain platforms. So, a game might come out on a few systems first, and then later on others. This often happens when a new game console is released, as developers need time to learn how to make games for it.

Some games might not be cross-platform because of special deals between game makers and console companies. For example, a game might be released only on a Sony PlayStation for a certain time, or even forever, if there's a special agreement.

Cross-Platform Play

Many game developers now let players on different systems play together online. This is called "cross-platform play." For example, players on an Xbox can play with friends on a PC. The first game to allow this was Quake 3.

Games that support cross-platform online play include Rocket League, Final Fantasy XIV, and Minecraft (with its Better Together update).

Cross-Platform Programming

Cross-platform programming is the skill of writing software specifically to work on more than one platform.

Approaches to Cross-Platform Programming

There are different ways to write a cross-platform app:

Separate Versions: One way is to create different versions of the software for each system. For example, the Windows version might have one set of code files, and the Mac version another. This can be more expensive and lead to more bugs.
Hiding Differences: Another way is to use special software that hides the differences between platforms. This "abstraction layer" makes the app not care about the specific platform it's running on. Apps that run on the Java Virtual Machine (JVM) are made this way.
Mixing Methods: Some apps use a mix of these methods. For example, the Firefox web browser uses abstraction for some parts, but also has separate code for platform-specific features like how the menus look.

Toolkits and Environments

Many tools help developers create cross-platform software:

Flutter: A popular tool from Google for making apps for Android and iOS.
Qt: A widely used tool for creating apps for Windows, macOS, Linux, and other systems.
Unity and Unreal: Popular tools for making cross-platform video games.
Kivy: An open-source tool written in Python for creating apps on Android, iOS, Linux, macOS, and Windows.
Lazarus: A programming environment that helps create apps for Linux, macOS, iOS, Android, and Windows.
wxWidgets: An open-source tool that works on Linux, Windows, and macOS.

Challenges

Developing cross-platform software can have its difficulties:

Testing: It's much harder to test cross-platform apps. Small differences between systems can cause unexpected problems or "bugs." Some developers joke it's "write once, debug everywhere."
Limited Features: Developers might have to use only the features that are available on *all* platforms. This can stop them from using the most advanced or unique features of a specific system.
User Interface: Different platforms have different ways of doing things in their user interfaces. For example, where the "OK" or "Cancel" button goes might be different. If a cross-platform app doesn't follow these rules, it can feel strange or "clunky" to users.
Performance: Scripts and virtual machine code sometimes run a bit slower because they need to be translated into the computer's native language each time they are used.
Security: Because they run on many systems, cross-platform environments can sometimes have security weaknesses that could affect users on different platforms.