Hey there, I see you're asking about different ARM architectures. As a programmer, I've worked with a few of these and can hopefully help clear things up. So, first things first, ARM (Advanced RISC Machines) is a type of processor commonly used in smartphones, tablets, and other devices.

Now, when it comes to disambiguating the different names, it can get a bit confusing. ARM9 is an older architecture, while ARMv9 is the latest and greatest, with lots of new performance features. A64 and Aarch64 are actually the same thing - they refer to the 64-bit version of the ARM architecture.

As for the A78, that's the latest and greatest in the mobile space, with even more performance improvements over the A64. But don't worry about feeling left behind - most software is still developed to run on a variety of architectures, so you don't need to be an expert in all of these.

But if you're interested in programming for ARM, you can check out some resources to get started on different architectures. There are lots of open source projects online that you can tinker with, and many professional development platforms will have tools available that make it easier to work with ARM processors. Happy coding!