白发齐眉

[color=Orange]1.钱不是问题，问题是没钱！
2.烧香的不一定是和尚，还可能是熊猫…
3.喝醉了我谁也不服,我就扶墙!
4.我就像一只趴在玻璃上的苍蝇，前途一片光明，但又找不到出路．
5.谁说我白、瘦、漂亮~我就跟他做好朋友~
6.关于丁字裤：以前，脱下内裤看屁股；现在，拔开屁股看内裤??
7."什么叫乐观派的人？""这个??就像茶壶一样，屁股都烧得红红的，他还有心情吹口哨！"
8.避孕的效果：不成功，便成人?
9.白天停水，晚上停电，发不出工资，买不起面，打开邓选找到答案，原来是社会主义初级阶段，翻到最后，我靠，一百年不变。
10.我一朋友在联通实习,一天,一老头走近来,劈头盖脸就来句"给我办张移动卡,好吧?"然后我那朋友头也不抬的就来句﹕"师傅,有人来砸场子[/color]

Unix is based on the standards set by a number of organizations. A Unix standard is an agreed system by which all concerned parties conduct their computing and that covers all areas of the Unix operating system. The Unix user should be familiar with the major standards that are in existence.
The Portable Operating Interface (POSIX) standard measures whether a system is portable or not. For example, a program has portability if you can take a program from a System V Unix system and easily rework it to run on a Berkeley Software Distribution (BSD) system.
The Institute of Electrical and Electronic Engineers (IEEE) has created a series of standards committees for the POSIX standards. The POSIX.1 committee standardizes the C library interface used to write programs for Unix. The POSIX.2 committee standardizes the commands available for the general user.
The X/Open series of standards was founded by the X/Open consortium of computer vendors, software suppliers, and customers in Europe. X/Open brings together various Unix-related standards including the current attempt at a Common Open System Environment (COSE) specification. X/Open publishes a series of specifications called the X/Open Portability Guide (XPG). This guide consists of publicly available reference documents that define the steps to be taken by application developers when coding and compiling programs.
The OSF standard was developed by the Open Software Foundation (OSF). This was a cooperative venture by several Unix vendors including Digital, Hewlett Packard, IBM, and others. The OSF is supported by leading computer suppliers, many customers, and government agencies.
The United States Government has specified a series of standards based on XPG and POSIX.
There are several different ways to access a Unix machine. The first way is through the use of a workstation or a personal computer (PC).
You can also use a dumb terminal to connect to a Unix machine. A dumb terminal consists of a monitor, or terminal, and a keyboard. Dumb terminals are suited to many applications where graphics are not required, such as database entry. They are also inexpensive and effective.
An X terminal consists of a monitor, a keyboard, and a mouse. The difference between an X terminal and a dumb terminal is that an X terminal provides the user with a graphical environment. You use the mouse to manipulate windows. The graphical interface used on X terminals is the X window System.
You can also use Unix over a network connection. Workstations, PCs, dump terminals, and X terminals can initiate either of the two types of network connections displayed on the screen (LAN Connection and Telnet Connection).
A standard feature of Unix that is common to all versions it the kernel. It is important to understand how the kernel works. The kernel is the system control process of the Unix operating system. It is the layer of software that interacts with the hardware.
The kernel executes programs by issuing instructions to the Central Processing Unit (CPU). It controls the allocation of computer hardware and memory and controls the peripheral devices connected to the computer. It also manages all computer resources.

The evolution of the Unix operating system began with the Multiplexed Operating and Computing System (MULTICS) project in 1965. This was a joint project between Bell Laboratories, General Electric, and Massachusetts Institute of Technology.
However, MULTICS became too complex and Bell Laboratories withdrew its participation in the project in 1969.
One of the researchers in Bell Laboratories, Ken Thompson, started writing programs that simulated the behavior of the MULTICS file system. In 1969, he wrote the first version of Unix, called the Unixplexed Operating and Computing System (UNICS). The Unix programs were coded in assembly language.
In 1973, Thompson, along with Dennis Ritchie, who wrote the first C compiler, made a significant change to the Unix operating system with the fifth edition. The kernel, which was originally coded in assembly language, was rewritten in the C language.
The use of the portable C language also made Unix portable to different machines by recompiling the code for the specific target hardware platform.
[quote]
1. BSD-> While at the University of Berkeley, Thompson wrote the first Berkeley version of Unix with students Bill Joy and Chuck Haley. This version was distributed to students, who worked on the source code. The final version that incorporated all the modifications was named BSD, meaning Berkeley Software Distribution. From BSD came virtual memory, Sendmail, and support for TCP/IP. Some examples of Unix products based on BSD are: Sun OS 4.x (SUN), ULTRIX (DEC), NextStep (NeXT), LINUX.
2. System V-> Bell Laboratories felt that Unix was a commercially viable product and charged for it’s licensing fees. The System V operating system was developed by a consortium of vendor to an agreed standard, which incorporated many features to make it more powerful, reliable, and secure. For several years, System V was the most conservative, commercial, and well-supported strain of Unix products. The two most recent releases of System V, Release 3 (SVR 3.2) and Release 4 (SVR 4), remain popular. All System V products that are based on work carried out at Bell Laboratories require a license from the current owner, Unix System Laboratories. Some examples of System V products are: Sun OS 5.x/Solaris (SUN), HP – UX (HP), AIX(IBM), IRIX(SGI), Digital Unix (DEC), SCO UNIXware.

[/quote]

Today, System V and BSD look very much alike. Then have a commonality of software, look and feel, and a broad set of features and commands.
Most versions of Unix have features of both System V and BSD, and users carry out tasks using BSD commands when that works best and System V commands at other times. Two of the main differences between the two versions are in the ways the ps and printing commands function.
The ps command reports the status of the current processes.


For more clear review, plz click the picture.

哎。怎么说也算是考证达人了，不过似乎面对考证，特别是国内的考证，真是一筹莫展。。
目前所有考出的证书基本上都是国外的认证考试，国内的就连计算机基础二级都没过，系分也是，明天的CPA-会计。。。。又是去过场的了。。。[cat]