Operating system
Operating system is a program that acts as an intermediary between a user of a computer and the computer hardware.
Operating system goals: Execute user programs and make solving user problems easier; make the computer system convenient to use; use the computer hardware in an efficient manner.
Take Linux for example, the Linux system is composed of three main bodies of code:
1.The kernel is responsible for maintaining all the important abstractions of the operating system, including such things as virtual memory and processes;
2.The system libraries define a standard set of functions through which applications can interact with the kernel, and which implement much of the operating system functionality that does not need full privileges of kernel code;
3.The system utilities are programs that perform individual, specialized management tasks.
Figure1. Components of the Linux system
As well-known similar features between UNIX and Linux, UNIX consists of two separable parts: the kernel and the system programs. We can view the UNIX operating system as being layered, as shown in Figure 15.Everything below the system-call interface and above the physical hardware is the kernel. The kernel provides the file system, CPU scheduling, memory management, and other operating system functions through system calls. System programs use the kernel-supported system calls to provide useful functions.
System calls define the application programmer interface (API) to UNIX; the set of system programs commonly available defines the user interface. The programmer and user interface define the context that the kernel must support.
Figure2. 4.3BSD layer structure
1. Open source resources
Linux is most wonderful open source activity:
2. Web pages
Radhat has a lot of useful information about Linux operating system: http://www.redhat.com/
3. Citations
<<Operating System Concepts>>and <<Applied Operating System Concepts>>, both come from: Abraham Silberschatz Peter Baer Galvin Greg Gagne, are good books on operating system principal.