They're not.
Perhaps since the advent of UNIX, it has become obvious that writing software in higher level languages makes for less debugging and more reliable code, but originally OSs were written in the assembler of the machine they ran on.
Believe it or not, most OS geeks think of "C" as a high level language. The fact that you can directly address all of memory and that it has a concept of interupt handling makes it an ideal candidate for portable OS code (consider that UNIX and later Linux now runs on virtually all hardware platforms).
Java specifically prevents you from directly accessing random memory. You can only address memory that Java has allocated to you in the form of objects. You can imagine writing a function that allowed java to directly access that memory ... but what would that function be written in? Probably C.
In fact, even version of the java engine I have seen was written in C or C++.
Way back when, the majority of programmers out there had experience with assemblers and C was such an advance that there was no reason to turn back.
By the way, the vast majority of OSs written in C still have a tiny bit of assembler associated with them associated with page handling and interupts.
In short C is the highest low level language, where you define "low level language" as one that can directly access memory by address instead of as an object. Alternately, you can say that C is high level language that has the advantage of being able to directly access memory by ... etc.
Problem is - the ability to talk about addresses instead of object handles makes it very easy to write bad code. And there is a LOT of bad C out there.
C and Assembly.
c
Mostly operating systems are developed by assembly languages and C. Windows operationg system is developed by Visual C++
Because Linux is "sort-of-a-copy-of-Unix" (which is not), and Unix was written in C. C was created to write Unix. Most portable operating systems or serious embedded devices are written in some incarnation of C and C++. Including MS-DOS and earlier copies of Window$ (which I am sure still uses it)
An operating system is mostly developed in C. C++ is less common, but used by several OS developers. There also is some operatingsystems developed in Pascal and Ruby. The last (ruby) used an interpreter in C. To load the operating system, you need a bootloader. Which is at least partially written in assembler.
Usually a combination of C++, C and assembly language.
Linux operating systems utilize many languages. The kernel is mostly written in C.
C and C++ are not directly supported by operating systems. You must use a compiler to convert a program written in C or C++ to a native executable that runs under a particular operating system. In other words, you can use C or C++ under any operating system for which a compiler exists for the desired language.
c language helps to create securities create several programs to build the software{operating systems.
C and Assembly.
c
Mostly operating systems are developed by assembly languages and C. Windows operationg system is developed by Visual C++
No. The bulk of the Windows operating system is written in C++.
There are many operating systems developed in C, the most notable of which is Linux.
The C programming language was originally created for Unix. Unix, and most other Unix-like systems such as Linux, are written almost entirely in C.
Because Linux is "sort-of-a-copy-of-Unix" (which is not), and Unix was written in C. C was created to write Unix. Most portable operating systems or serious embedded devices are written in some incarnation of C and C++. Including MS-DOS and earlier copies of Window$ (which I am sure still uses it)
The Unix operating system. The first versions of the Unix operating system were written in the "B" language, and later written in "C", which was invented in order to develop Unix on the PDP-11 machine.