For programming only in ASM is too hard and the OS is in fact at some places that can be programmed by C linked to ASM.
Mac OS X is written in the programming languages C and Objective C.
C programming language
Like C, it is used when a low-level programming language is necessary. While C++ is commonly used for graphics-heavy software such as games, photo and video editing apps, browsers, C is more widely used for embedded devices and OS kernels.
C is considered a high-level programming language.
C and C++ are both high-level programming languages.
C is not an operating system, but a programming language. An OS is a piece of software that sits between other software and hardware, facilitating communication between applications and devices, in an uniform way. A programming language is a set of rules, like the English grammar. Any text that satisfies the rules can be compiled, resulting in a piece of software that can then be run in an OS. C is such a programming language, popular for systems and other low level programming. It is notorious for its portability (you can write code in C and compile it for many OS's), flexibility and degree of control offered to programmer. Also notable is the fact that many OS's are originally written in C or it's off-shoot C++.
C++ is used in virtually every field of programming, including gaming and multimedia, financial, scientific and industrial applications, as well as low-level subsystem programming.
Android, Symbian, Blackberry OS (RIM) : java iOS uses OPP-C ( C#/C++)
Microsoft Windows Was Created By Using C, C++, Visual BASIC
Use "OS Shell" from File menu.
Programming.
It is a Linux-based open source operating system. Programming languages are in C, C++, and Java, with apps being written in a customized version of Java.