The 6502 was a great CPU for its time and price point. I wrote many programs in its assembly language. However, if you're going to work on modern systems, there are too many differences for the 6502 to be a good first assembly language (unless the 6502 is your focus).
The 6502 was designed to be easily implemented with relatively few transistors. For that it was amazing. There is a reason it was popular! But its CPU registers are only 8-bit, its call stack is 256 bytes, and for real work you need to use the zero page (zpage) well. None of these are likely to relevant to a modern software developer using assembly. Its design encourages the use of global locations, again, an approach that don't make sense on modern systems.
I say this as someone who admires what the 6502 was able to achieve in its time, and I even have a long-running page dedicated to the 6502: https://dwheeler.com/6502/
If you want retro and easy, the 68000 has it beat in terms of simplicity of development. The 68K is quite regular & a little more like modern systems (sort of).
However, I think starting retro is often a disservice. Most the time the reason to use assembly is performance. If you're running code on chips more than a dollar or so, getting performance out of modern architectures is MUCH different than retro computers. For example, today a lot depends on memory cache latency, yet is typically not a serious concern on most retro computers. So learners will learn to focus on the wrong problems.
If you want a modern simple architecture, may I suggest RISC V? That's under a royalty-free open source license, and real computers use it today. It's pretty simple (your basic load-store architecture) and you can pick only the modules you care about. Full disclosure: I work for the Linux Foundation, but I'd say that anyway.
Plausible alternatives are ARM and x86. If you subset them, they're okay.
The reality is that assembly languages reflect the underlying system, and that will change over time.
The 6502 was designed to be easily implemented with relatively few transistors. For that it was amazing. There is a reason it was popular! But its CPU registers are only 8-bit, its call stack is 256 bytes, and for real work you need to use the zero page (zpage) well. None of these are likely to relevant to a modern software developer using assembly. Its design encourages the use of global locations, again, an approach that don't make sense on modern systems.
I say this as someone who admires what the 6502 was able to achieve in its time, and I even have a long-running page dedicated to the 6502: https://dwheeler.com/6502/
If you want retro and easy, the 68000 has it beat in terms of simplicity of development. The 68K is quite regular & a little more like modern systems (sort of).
However, I think starting retro is often a disservice. Most the time the reason to use assembly is performance. If you're running code on chips more than a dollar or so, getting performance out of modern architectures is MUCH different than retro computers. For example, today a lot depends on memory cache latency, yet is typically not a serious concern on most retro computers. So learners will learn to focus on the wrong problems.
If you want a modern simple architecture, may I suggest RISC V? That's under a royalty-free open source license, and real computers use it today. It's pretty simple (your basic load-store architecture) and you can pick only the modules you care about. Full disclosure: I work for the Linux Foundation, but I'd say that anyway.
Plausible alternatives are ARM and x86. If you subset them, they're okay.
The reality is that assembly languages reflect the underlying system, and that will change over time.