Shulou(Shulou.com)06/03 Report--

The two inventors of UNIX system are Ken Thompson and Dennis M. Ritchie of Bell Labs. The Unix system was invented in 1969-1970 and rewritten with C in 1971.

Since about 1985, UNIX has gradually formed two main schools:

BSD: Berkeley's leading representative of open UNIX

SystemV:AT&T leads the commercial version of UNIX

Other UNIX distributions are basically based on BSD or SystemV

1 major UNIX derivatives and their genres

Name

Company

School

AIX

IBM

BSD SystemV

AOS

IBM

BSD

HP-UX

HP

SystemV

SCO UNIX

SCO

SystemV

Solaris

SUN

BSD SystemV

UNIX

AT&T

SystemV

Xenix

Microsoft / SCO/Altos

SystemV

2 online documentation

FreeBSD documents: http://www.freebsd.org/zh_CN/docs.html

AIX: http://www-03.ibm.com/systems/power/software/aix/

Solaris:

Http://www.oracle.com/us/products/servers-storage/solaris/solaris11/resources/index.html

HP-UX:

Http://h27007.www1.hp.com/us/en/business-critical/operating-environments/hpux11i/index.aspx#tab=TAB1

OpenBSD: http://www.openbsd.org/faq/faq4.html

NetBSD: http://www.netbsd.org/docs/

3 domestic third-party websites

UNIX Technology Network: http://www.chinaunix.net/

Home for UNIX enthusiasts: http://unix-cd.com/

51CTO operating system Channel: http://os.51cto.com/

4 the concept of kernel

The kernel is a very important concept in the operating system. The kernel is the core of the operating system, its status is similar to the human brain, its main role is responsible for managing system resources, is the most basic part of the operating system. The main services provided by the kernel are as follows:

Memory management: including physical memory and virtual memory

Process management: including creating, scheduling, and terminating processes

Process communication: including communication between local processes and processes of different hosts on the network

Input and output: data exchange between device drivers and computer hardware

File management: including file system and disk file management

5 two main types of kernel

1) single kernel: a huge executable file, which includes many modules with different functions, such as memory management, process management, process communication and so on. The design of single kernel makes the communication between different modules can be realized by calling the function of the corresponding module, and the execution efficiency is very high. However, the difficulty of its own design and implementation is very high, and because of its high code integration and coupling, when there is a problem in one of the modules, it will often affect the normal work of other modules, and eventually affect the normal work of the whole kernel. FreeBDS and Linux use single kernel architecture.

2) microkernel: compared with the single kernel, the design idea of the microkernel is just the opposite. The function of the kernel is simplified, generally providing only basic operating system services, while other functions are separated and designed as separate system services. The services are relatively isolated and exist in the operating system in the form of different processes. Communication between processes is accomplished through message passing. The execution efficiency of this design is not as high as that of a single kernel, but its reliability is guaranteed. When something goes wrong with a system call, it doesn't affect the kernel, so it doesn't affect the whole system. The one that uses the microkernel architecture is AIX.

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