How do developers code unique software?

Actually it sounds like you don't know anything at all about programming. This is like asking how you can use math on numbers you've never seen before. Programming is about creating logical steps to manipulate information and device(s). Anything the device can do, you can control it with code. Any information that can be created, you can create it with code. You write the steps to make those work together in any creative ways you can think of. If your question is really "how do you know how to do that" it comes down to what problems you're trying to solve or things you're trying to accomplish. I'm the very early days of programming, the programmers had to do everything by hand and write what's called *machine code/language* to directly control the computer in the language it understands (binary). The computer only understood certain instructions and only 1 type of data (bytes). As long as you had documentation on the computer's machine code instruction set, you could program it. The next generation came a new language called *Assembly* which was an alphabetic language of instruction sets that was human readable and could be directly translated into machine code. This was easier for programmers because they could use English-sounding words to write and read code instead of just binary numbers. The breakthrough came in the next generation with the first real programming languages. These were English language instructions that read almost like sentences. They were designed in a way that matched the way humans think about explaining steps to other people to control information, numbers, and device settings. This was revolutionary because you now had a universal set of English instructions that were intuitive, could be learned quickly, and could be used on more than one type of computer. The only caveat here was you needed a special type of program to translate your programming language you wrote into machine language. This is called a **compiler**, and it needed to be run every time you changed your program. Since the compiler translates your program into machine language, and nearly every type of computer had its own language, there had to be a compiler created for every combination of programming language + computer that you needed to work with. This spawned specialty languages and computers, because it's not worth the time to write compilers for every combination. Virtually all programming today follows that model in some way. All of the advances in programming that have happened since then have added layers of *abstractions* over previous generations of abstractions to make it easier for us to write code without having to worry about how the individual device is going to handle it. One of the big break-throughs that happened during all of that was the standardization of operating systems. These were a permanent layer of abstraction pre-installed on computers that standardized the programming languages and instructions to run on those devices. The reason this was such a big deal was because the OS created its own layers of abstractions that meant the compilers no longer had to worry about the individual devices themselves. Instead they were written for the operating system. And the OS then made the compiled code work on whatever device it was running on. This opened the door for thousands of new computer manufacturers to allow programmers to easily write applications for their devices. The only thing they had to worry about was making the computer work for the target operating system. In later years that effort became a collaborative one between the creators of the OS's and the manufacturers of the various devices. Instead of trying to make devices from scratch that fit the nuances of the OS, the OS's started publishing easy-to-follow guides called Device Development Kits (DDKs) that gave device makers some tools and step by step guides. This opened the door even more to allow device makers to support operating systems. On the software side, both the OS makers and device manufacturers started publishing Software Development Kits (SDKs) to provide a similar set of tools and instructions for creating new software that ran on those devices and OSs. Often, programmers began realizing they were writing some of the same code to do the same things, or they were writing code that was so difficult and took so long to create properly that they didn't want to have to go through that every time. Instead they started creating *Libraries* from this code to make the code reusable by themselves and other programmers. Any time they needed to so the same thing again, they'd just import that library, and it was like the code was pre-written for them. To bring together all these various tools (Compilers, SDKs, Libraries, etc) for the programmers, specialized tools were created called Interactive Development Environments (IDEs) to simplify this whole processes. These are applications we use to write and test code that automate most of those other things in the background like compiling, syntax checking, and utilizing SDKs. Nearly all modern software is written in some form of an IDE. All of that effort has brought us to today. To write programs in 2024, we almost always use an IDE and sets of libraries (pre-written code) that are built into the OS, we've used before, downloadable for free, or available to purchase. Modern programmers use libraries for just about anything you can think of now. We write code in 10 minutes that might have taken a week 50 years ago to do the same thing. So programming skill today is just as much about knowing which libraries and frameworks to use and how to use them as it is about writing custom code ourselves. This is an oversimplification, but the biggest take you should get from this is that programming is very much a *creative* process of using your imagination to solve problems and create things from scratch. We're like artists, and the computer is our canvas. The languages are our paints.