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portability.md
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# Portability
Portable [software](software.md) is software that is easy to [port](port.md) to (make run on) other platforms. Platforms here mean anything that serves as an environment enabling software to run, i.e. [hardware](hardware.md) platforms ([CPUs](cpu.md), [ISAs](isa.md), game consoles, ...), different [operating systems](os.md) vs [bare metal](bare_metal.md), [fantasy consoles](fantasy_console.md) etc. **Portability is an extremely important attribute of [good software](lrs.md)** as it allows us to write the program once and then run it on many different computers with little effort -- without portability we'd be constantly busy rewriting old programs to run on new computers, portability allows us to free our programs from being tied to specific computers and exist abstractly and independently and so become [future proof](future_proof.md). Examples of highly portable programs include [Anarch](anarch.md), [Simon Tatham's Portable Puzzle Collection](stppc.md), [sbase](sbase.md) (suckless) implementation of Unix tools such as [cat](cat.md) and [cmp](cmp.md) etc.
Portable [software](software.md) is software that is easy to [port](port.md) to (make run on) other [platforms](platform.md). Platforms here mean anything that serves as an environment enabling software to run, i.e. [hardware](hardware.md) platforms ([CPUs](cpu.md), [ISAs](isa.md), game consoles, ...), different [operating systems](os.md) vs [bare metal](bare_metal.md), [fantasy consoles](fantasy_console.md) etc. **Portability is an extremely important attribute of [good software](lrs.md)** as it allows us to write the program once and then run it on many different computers with little effort -- without portability we'd be constantly busy rewriting old programs to run on new computers, portability allows us to free our programs from being tied to specific computers and exist abstractly and independently and so become [future proof](future_proof.md). Examples of highly portable programs include [Anarch](anarch.md), [Simon Tatham's Portable Puzzle Collection](stppc.md), [sbase](sbase.md) (suckless) implementation of Unix tools such as [cat](cat.md) and [cmp](cmp.md) etc.
**Portability is different from mere [multiplatformness](multiplatform.md)**: multiplatform software simply runs on more than one platform without necessarily being designed with high portability in mind; portable software on the other hand possesses the inherent attribute of being designed so that very little effort is required to make it run on wide range of general platforms. Multiplatformness can be achieved cheaply by using a [bloated](bloat.md) framework such as the Godot engine or [QT](qt.md) framework, however that will not achieve portability; on the contrary it will hurt portability. Portability is achieved through good and careful design, efficient code and avoiding [dependencies](dependency.md) and [bloat](bloat.md).
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## How To Make Portable Programs
In short: use [abstraction](abstraction.md) to not get tied to any specific platform (separate [frontend](frontend.md) and [backend](backend.md)), minimize [dependencies](dependency.md) (minimize use of [libraries](library.md) and requiring hardware such as [floating point](float.md) unit or a [GPU](gpu.md), have [fallbacks](fallback.md)), write efficient, [simple](kiss.md) code (lower hardware demands will support more platforms), avoid platform-specific features (don't write in [assembly](assembly.md) as that's specific to each CPU, don't directly use [Linux](linux.md) [syscalls](syscall.md) as these are specific to Linux etc.).
In short: use [abstraction](abstraction.md) to not get tied to any specific platform (separate [frontend](frontend.md) and [backend](backend.md)), [keep it simple](kiss.md), minimize [dependencies](dependency.md) (minimize use of [libraries](library.md) and requiring hardware such as [floating point](float.md) unit or a [GPU](gpu.md), have [fallbacks](fallback.md)), write efficient, [simple](kiss.md) code (lower hardware demands will support more platforms), avoid platform-specific features (don't write in [assembly](assembly.md) as that's specific to each CPU, don't directly use [Linux](linux.md) [syscalls](syscall.md) as these are specific to Linux etc.).
Remember, portability is about making it easy for a programmer to take your program and make it run elsewhere, so portability is about constantly putting oneself in the shoes of someone else with a very different computer and asking questions such as "how hard will it be to make this work if this library isn't available?". Even things that are supposed or commonly expected to be present on all platforms, such as a file system or a raster screen, may not be present on some computers -- always remember this.
**Do NOT use big frameworks/engines** -- it is one of the greatest misconceptions among many programmers to think portable software is created with big frameworks, such as the [Godot](godot.md) engine, which can "single click" export/deploy software to different platforms. This will merely achieve creating a badly [bloated](bloat.md) multiplatform program that's completely dependent on the framework itself which drags along hundreds of [dependencies](dependency.md) and wastes computing resources (RAM, CPU, storage, ...) which are all factors directly contradicting portability. If you for example create a snake game in Godot, you won't be able to port it to [embedded](embedded.md) devices or devices without an operating system even though the snake game itself is simple enough to run on such devices -- the game drags along the whole Godot engine which is so huge, complex and hardware demanding that it prevents the simple game from running on simple hardware.
**Do NOT use big frameworks/engines** -- it is one of the greatest misconceptions among many inexperienced programmers to think portable software is created with big frameworks, such as the [Godot](godot.md) engine or the [QT](qt.md) framework, which can "single click" export/deploy software to different platforms. This will merely achieve creating a badly [bloated](bloat.md) multiplatform program that's completely dependent on the framework itself which drags along hundreds of [dependencies](dependency.md) and wastes computing resources (RAM, CPU, storage, ...) which are all factors directly contradicting portability. If you for example create a snake game in Godot, you won't be able to port it to [embedded](embedded.md) devices or devices without an operating system even though the snake game itself is simple enough to run on such devices -- the game drags along the whole Godot engine which is so huge, complex and hardware demanding that it prevents the simple game from running on simple hardware.
**The same goes for languages and [libraries](library.md)**: do NOT use big/bloated languages such as [Python](python.md), [Java](java.md) or [JavaScript](javascript.md) -- your program would immediately become dependent on a hugely complex ecosystem of such language. For portability you should basically **only write in [C](c.md)** (the best established, time tested, relatively simple language supported basically by every platform) or in [C++](cpp.md) at worst, and even with these languages do NOT use the newer standards as these hugely limit the number of compliant compilers that will be able to compile your program. The best is to write in C89 or C99 standard of C. **Minimize the number of libraries you use**, even if it is the standard library of your language -- not all compilers fully adhere to standards and some don't have the standard library even if the should.