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Key APIs from the Macintosh Toolbox would be implemented in Mac OS X to run directly on the BSD layers of the operating system instead of in the emulated Macintosh layer. This modified interface, called Carbon , would eliminate approximately 2000 troublesome API calls (of about 8000 total) and replace them with calls compatible with a modern OS.
Operating System Concepts by Abraham Silberschatz and James Peterson is a classic textbook on operating systems. It is often called the "dinosaur book", as the first edition of the book had on the cover a number of dinosaurs labeled with various old operating systems. The bigger dinosaurs were labeled with the older big OSs.
Service definitions, like the OSI model, abstractly describe the functionality provided to a layer N by a layer N−1, where N is one of the seven layers of protocols operating in the local host. At each level N , two entities at the communicating devices (layer N peers ) exchange protocol data units (PDUs) by means of a layer N protocol .
The operating system provides an interface between an application program and the computer hardware, so that an application program can interact with the hardware only by obeying rules and procedures programmed into the operating system. The operating system is also a set of services which simplify development and execution of application programs.
A monolithic kernel is an operating system architecture with the entire operating system running in kernel space. The monolithic model differs from other architectures such as the microkernel [1] [2] in that it alone defines a high-level virtual interface over computer hardware. A set of primitives or system calls implement all operating system ...
An operating system abstraction layer (OSAL) provides an application programming interface (API) to an abstract operating system making it easier and quicker to develop code for multiple software or hardware platforms. It can make an application less dependent on any one specific operating system.
Unix systems use a centralized operating system kernel which manages system and process activities. All non-kernel software is organized into separate, kernel-managed processes. Unix systems are preemptively multitasking : multiple processes can run at the same time, or within small time slices and nearly at the same time, and any process can ...
This is the mode in which the operating system usually runs." [12] In a monolithic kernel, the operating system runs in supervisor mode and the applications run in user mode. Other types of operating systems, like those with an exokernel or microkernel, do not necessarily share this behavior. Some examples from the PC world: