Thread: C, C++ difference - getting confused

I'll try to answer some of those briefly as I understand it.
1. You still won't find a *good* C++ compiler for a lot of platforms as it is a huge and complicated language to implement. On the other hand, because the language is complicated, the user code becomes much simpler in most cases.
2. Other than extremely resource constrained systems, I can't think of anything.
3. Try and see. It becomes a mess, at least that was my brief experience with the GTK+ library, which does some sort of OOP in C.
4. Some features in C++ have no direct equivalent in C. Consider templates for example. Macros can barely touch what can be achieved with templates.

Originally Posted by s5s

"Oh you can't use C++ for that, you need to learn C."

except in cases where you're required to use C, per the project specifications, and on platforms that do not have a C++ compiler, this is a completely false statement. whoever said this to you clearly does not understand the relationship between C and C++.

Thank you. To answer my questions I will put this in (I had read it before):

When to use C over C++, and C++ over C? - Programmers Stack Exchange
Is the C programming language still used? - Programmers Stack Exchange

I sort of knew this. What I didn't know (and didn't get) is why (the hell) is everything in linux written in C?

I am a supporter of keeping things as simple as possible and since C is a simpler language I thought that they were just using C because small utilities (e.g. coreutils) don't really need to be in C++, so why add the complication and restriction (as mentioned C++ is available on a limited number of systems).

However, I've also seen very complex software that is written in C, rather than C++ (e.g. opencv).

Originally Posted by s5s

C++ is available on a limited number of systems

I think that the use of "a limited number" here should be replaced with "not all." C++ is available on any platform supported by gcc. and that is a lot of platforms. these days, gcc supports just about any system that you can plug a keyboard and monitor into.

Originally Posted by s5s

However, I've also seen very complex software that is written in C, rather than C++ (e.g. opencv).

C code tends to be more verbose, because the language has fewer built-in abstractions, requiring the programmer to do more.

Not everything in Linux is written in C. The Linux kernel is written in C and the person that controls that source code programs in C and doesn't like C++ so the Kernal is in C. However many other applications are written in C++. For example the KDE Windowing system is based on C++ not C. And don't forget that most of the Windows kernel is also written in C.

Jim

Originally Posted by jimblumberg

Not everything in Linux is written in C. The Linux kernel is written in C and the person that controls that source code programs in C and doesn't like C++ so the Kernal is in C. However many other applications are written in C++. For example the KDE Windowing system is based on C++ not C. And don't forget that most of the Windows kernel is also written in C.

Jim

Thanks for the answer Jim.

Yes, exactly - kernels are always written in C. Nobody ever uses C++. I'm not certain why. I mean I know why to a certain extent but I don't know the full list of reasons why C++ is not used. Sure you can't use exceptions, "new", "delete" etc. but templates and classes would be useful, I would have thought.

A lot of people claim C++ hides function calls. I don't think it hides them. I think it abstracts them. I think C often can hide information (e.g. void pointers, cpp abuse etc.).


And yes I mean a windowing system is a classic example of where C++ will be used (OOP).

A good example of a project that converted from C to C++ (complete rewrite) is ns (network simulator). They switched from C to C++ when going from ns-2 to ns-3.

For future (and current) readers - I'm not comparing C to C++ in absolute terms. I think each language excels in a particular area and I'm trying to find those areas so that I can have a feeling of when to use C and when C++ and spot "mistakes" i.e. when C would have been a better match rather than C++.

I also think when people say C or C++ they also attach a meaning relating to the purpose of the code rather than the language itself. You could very well write valid C++ code but still call it C because of how it's used (e.g. in a kernel, on a microcontroller etc.).

Originally Posted by manasij7479

What ?
Unless you are only talking about the kernel, there is a lot of C++ nowadays.
In my system, C is used by the kernel and the gnu userspace and a few utilities like git...that makes about 50 packages .
Now, KDE (about 400 packages, excluding docs and artwork), Firefox , Blender, GCC, clang+llvm, Libre Office, all Linux games I have played are written in C++.

[Didn't notice the last post before posting..sorry]

Sorry I should have made it more clear - I was referring to GNU/linux software (packages). I wasn't referring to other projects (such as Gnome, KDE, XFCE etc) which can be in any language.

Honestly, you never need to use C. You can write a C-like program, compile it with a C++ compiler, and it will likely have fewer bugs than the equivalent C program. C++ does much stronger type checking, so that when you're casting from one pointer type, it will yell at you if you don't do an explicit cast.

It would be a mistake to say that kernels are never written in C++. You certainly can use exceptions and new/delete, but you have to set up for them first. There is no standard library for kernels. You would have to write it yourself.

Yes, exactly - kernels are always written in C. Nobody ever uses C++.

This is not necessarily true. Yes Linux is in C, for the previous stated reasons. And Windows was written in C because Windows predates C++. Probably one of the biggest stumbling blocks to creating an operating system from C++ is the size of the language it's self. C is a much smaller language, therefore easier to implement. But even historically C based programs are now being converted to C++, for example gcc is now being compiled as a C++ program.

Sure you can't use exceptions, "new", "delete" etc. but templates and classes would be useful, I would have thought.

Trying to use templates in a kernel can be fraught with danger. Remember a template is compiled only when it is actually used. And classes can also be problematic for a kernel, remember when writing a kernel you will usually not have the full language available. Many of the standard functions require support from the kernel so until the kernel initializes all the required components that are required for standard functions they are not available.

Jim

Originally Posted by s5s

Sorry I should have made it more clear - I was referring to GNU/linux software (packages). I wasn't referring to other projects (such as Gnome, KDE, XFCE etc) which can be in any language.

I can't see any difference.
There is no standard "GNU/Linux software packages", just a bunch of distinct projects .
And Android's user space for Linux, other than the few components they did not bother to reinvent , is almost entirely written in Java.
You need to get over the mentality that something can be written only in C.