Why is C used for writing drivers and OS codes? [closed] - c

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Why is C used for writing drivers and OS codes?
Is there a size problem?
Are there any drivers written in other languages?
Which language were XP, Vista, and Solaris written in?

Answer 1

C compiles down to machine code and doesn't require any runtime support for the language itself. This means that it's possible to write code that can run before things like filesystems, virtual memory, processes, and anything else but registers and RAM exist.

Answer 2

In safety-critical environments (think avionics, spacecraft, medical devices, transportation, control software for process control), systems (as well as drivers) are often written using Ada or even SPARK/Ada.
To clarify: C is usually understood to be fairly low level, and pretty much like a "macro language" for assembly itself, that's also where its power is coming from (speed, size, portability).
Ada, on the other, hand has been specifically designed for safety-critical applications with verifiability in mind, to quote Ada 2005 for Mission-Critical Systems:
Ada [9] is the language of choice for many critical systems due to its careful design and the existence of clear guidelines for building high integrity systems [10]
That's also where Ada's support for strong typing comes in, as well as a number of other important features (quoting design for safety):
Programming languages differ wildly in
their appropriateness for use in
safetyrelated systems. Carré et al.
identified six factors that influence
the suitability of a language for
high-integrity applications [Carré
1990]. These are:
Logical soundness
Complexity of definition
Expressive power
Security
Verifiability
Bounded time and space constraints
No standard programming language performs
well in all these areas although some
(such as Pascal and Ada) perform much
better than languages such as C or
C++. In highly critical applications
‘verifiability’ is of great
importance. Certain languages allow
powerful software verification tools
to be used to perform a wide range of
static tests on the code to detect a
range of programming errors.
[...] An
important issue in the selection of a
programming language is the quality of
the available compilers and other
tools. For certain languages validated
compilers are available. While not
guaranteeing perfection, validation
greatly increasing our confidence in a
tool. Unfortunately, validated
compilers are only available for a
limited number of languages, such as
Ada and Pascal. In addition to
compilers, developers of critical
systems will make use of a range of
other tools such as static code
analysis packages. The static tests
that can be performed on a piece of
code vary greatly depending on the
language used. To aid this process it
is common to restrict the features
that are used within certain languages
to a ‘safe subset’ of the language.
Well structured and defined languages
such as subsets of Ada, Pascal and
Modula-2 allow a great many tests to
be performed such as data flow
analysis, data use analysis,
information flow analysis and range
checking. Unfortunately many of these
tests cannot be performed on languages
such as C and C++ .
It would be really beyond the scope of this question to go into even more detail, but you may want to check out some of the following pointers:
Ada compared to C and C++
Ada vs. C
Quantifying the Debate: Ada vs. C++
Why choosing Ada as a teaching language? (Ada vs. C in University)
Comparing Development Costs of C and Ada (summary)
C / C++ / Java Pitfalls
& Ada Benefits
Is Ada a better C?
Ada, C, C++, and Java vs. The Steelman
Ada: Dispelling the Myths
Real-time programming safety in Java and Ada
If anyone wants to look into Ada some more, check out this: Ada Programming (wikibooks)
There are even programming languages that are specifically developed for highly critical applications, such as JOVIAL or HAL/S, the latter of which is used by the space shuttle program.
Is there any drivers written in any other languages?
I have seen some Linux drivers for special hardware being written in Ada, don't know about other operating systems though. However, such drivers usually end up wrapping the the C API.

Answer 3

Because C has the best combination of speed, low memory use, low-level access to the hardware, and popularity.
Most operating systems have a kernel written in C, and applications on top of that written in either C, C++, C# or Obj-C

Answer 4

C is by far the easiest language(other than assembly) to "get going" on bare bones hardware. With C, (assuming you have a 32bit bootloader such as GRUB to do the hard mode switching) all you must do is make a little crt0.asm file that sets up the stack and that's it(you get the language, not including libc). With C++ you must worry about dynamic casts, exceptions, global constructors, overriding new, etc etc.. With C# you must port the .Net runtime(which on it's own basically requires a kernel) and I'm not sure about Obj-C, but Im sure it has some requirements also...
C is simply the easiest language to use for drivers. Not only is it easy to get started with, but also it's easy to know exactly what happens at the machine level. Their is no operator overloading to confuse you and such. Sure it's handy in a "good" environment, but in Ring 0 where a bad pointer not only crashes your application, but usually results in a triple fault(reboot), blue screen, or kernel panic. You really like knowing what goes on in your machine..

Answer 5

"why we are using C language for writing drivers and OS codes.?"
So that programmers won't have to learn new syntax of each new assembly language for each new kind of machine.
"Is there any drivers written in any other languages?"
Historically, assembly languages. I don't remember if PL/S or BLISS could be used for drivers. Maybe B. In modern times, a few brave people use C++ but they have to be very careful. C++ can be used a bit more easily in user mode drivers in some situations.

Answer 6

Lisp machines had their operating systems written in Lisp, which shows that you don't have to use C or assembly. The Lisp machine business was destroyed by the availability of cheap PCs, whose operating systems were of course written in C and assembly.

Answer 7

C was one of the very first languages (that wasn't assembly) that was suitable for writing operating systems, so it caught on early. While other languages have appeared since that are also suitable for writing operating systems in, C has remained popular perhaps due to its long history and the familiarity programmers have with its structure and syntax.

Answer 8

C is also a language that teaches a lot about memory management and is low-level enough to show the barrier between hardware and software. This is something that is rare among many methodologies today, that have grown more towards abstraction way above anything at the hardware level. I find C is a great way to learn these things, while being able to write speedy code at the same time.

Answer 9

Remember that C was originally developed for writing operating systems (in this case - Unix) and similar low-level stuff. It is wery close to the system architecture and does not contain any extra features that we want to control, how they exactly work. However, please note that the rest of the operating system, including the programming libraries, does not have to be written in the same language, as the kernel. The kernel functions are provided through a system of interrupts and in fact such programming libraries can be written in any language that supports assembler snippets.
The most popular operating system nowadays are written in C: Windows, Linux and many other Unix clones, however this is not the rule. There are some object-oriented operating systems, where both the kernel and the programming interface are written in an objective language, such as:
NeXTSTEP - Objective-C
BeOS - C++
Syllable - C++
See: Object-oriented operating system on Wikipedia
Note that in Linux, it is possible to write kernel drivers in the languages other than C (however, it is not recommended). Anyway, everything becomes a machine code when it comes to running it.

Answer 10

"C compiles down to machine code and doesn't require any runtime support for the language itself."
This is the best feature of C

Answer 11

It's my belief that languages like Python, Java, and others are popular mainly because they offer extensive standard libraries that allow the programmer to code a solution in less lines. Literally a ruby programmer can open and read a file in one line where in C it takes multiple lines. However beneath this abstraction are multiple lines. Therefore the same abstraction be done in C and it's recommended. Oddly it seems the C philosophy is not to reduce the total lines of code so there is no organized effort to do so. C seems to be viewed as a language for all processor chips and naturally this means that it's hard to create any 'standard' abstracted one line solutions. But C does allow you to use #ifdef preprocessor commands so in theory you can have multiple variations of an implementation for multiple processors and platforms all on one header file. This can't be the case for python, or java. So while C does not have a fancy standard library it's useful for portability. If your company wants to offer programs that run on computers, embedded, and portable devices then C is your choice language. It's hard to replace C's usefulness in the world.

Answer 12

As another note for machines that have drivers in other languages, there is the SunSpot robotics platform. Drivers for devices that are connected (sensors, motors, and everything else that can communicate via the I/O pins) are written in Java by the user.