C and C++ are in many ways increasing not decreasing. C and C++ both have significant offerings in many areas, and you can find both in almost all industries.
I am guessing by the way you worded your question that you are being at least slightly dismissive of the embedded market. Many people are, but almost everything you touch has a microprocessor that likely is running some C and/or C++ code on it now.
Every cable box usually is C/C++, every DVR, home theater receivers, microwaves, conventional ovens, garage door controllers, hell even that stupid sink faucet you touch to turn on/off is likely running some C code. It is everywhere because it is the one language that is the most transportable and powerful across domains that carries the least amount of baggage with it.
C++ is less likely to be found on the tiny to small chips running things, but you see it more and more where chips can support it. Not to mention, every time you use your cell phone you are using dozens of components, most all written in C/C++ and not all are embedded systems.
I am not an expert in regards to FORTH so I'd have to let someone with more experience say. FORTH from what I know has been around since at least the Z80 days. But honestly, I do not know if it carries more or less baggage, nor whether it is really more portable.
All the embedded work I have done has mostly been C with a little more C++ in the recent years, outside of some machine level stuff for highly specialized devices. So just from that, at least in my experience C is the more common, portable and easily worked with language.
Every software that's widely used and isn't a crap gimmick is written in C/C++.
Android/Linux is mostly C. Google Search-C++. Web browsers-C++. Java VM is a c++ program. Games-C++.
The only place Java/Ruby/Python/etc has a foot hold is in websites providing crap gimmics that are just wrappers over C/C++ programs. Like uploading a photo or tweet, just providing some glue over all the C/C++ programs that actually do the work.
Anyone who needs performance. Although, if you really need performance, you're using C, not C++. Game engines are all written in C/C++. All those languages like Python and Javascript are all written in C/C++.
> Although, if you really need performance, you're using C, not C++.
Howso? Yea, don't do dynamic dispatch in your core performance critical loops, but templates give you a lot of capability to get nice abstractions without major (runtime) performance hits.
Almost anyone who does any cross platform development. C/C++ makes it very easy to write cross platform libraries that almost all platforms can consume.
There are hundreds of sectors where it is used daily , it is not popular in web and mobile app development , but I feel thats not the only place where typical "software development" happens .
ATMs , OS development , cellular networks , lots of industry specific desktop applications for petroleum industry , Cutting machine softwares (lathes , cnc etc) are written in cpp .
Insurance companies develop HPC stochastic financial projection models in C++. I have seen approaches using R or Python, but they couldn't give the performance necessary for getting results in reasonable time.
I do, when it's the right tool for the job. When in Rome, do as the Romans. Everywhere else, use C or C++. Why? I'm more comfortable and productive with it. I'm sure the Esperanto advocates wonder why I still speak English, too.
Most middle-ware systems like database/messaging/file system are written in C++. Users of such systems most likely develop their applications in C++ as well, like gaming and financial firms.
I am guessing by the way you worded your question that you are being at least slightly dismissive of the embedded market. Many people are, but almost everything you touch has a microprocessor that likely is running some C and/or C++ code on it now.
Every cable box usually is C/C++, every DVR, home theater receivers, microwaves, conventional ovens, garage door controllers, hell even that stupid sink faucet you touch to turn on/off is likely running some C code. It is everywhere because it is the one language that is the most transportable and powerful across domains that carries the least amount of baggage with it.
C++ is less likely to be found on the tiny to small chips running things, but you see it more and more where chips can support it. Not to mention, every time you use your cell phone you are using dozens of components, most all written in C/C++ and not all are embedded systems.