This section tries to present some basic knowledge about operating system, although it appeared in the 70s, gave “ideas” of many designers of operating systems and began to impose increasingly more reliable solution that and cost for interconnection of computer systems. Purpose of presenting UNIX system is to learn something useful for each activity in the County Information Centre, to bring up the lab on those who used their accounts for months and … (otherwise you can also find them). In addition, why not, you can earn money from a network management…
Brief History of UNIX system
The first version of UNIX was developed in 1969 by Ken Thompson and Denis Ritchie in the research group at Bell Laboratories, was written to run on a PDP-7 computer. The second version was written for the PDP 11/20 computer.
The third version, yet commercial, is completely written in C language for the PDP 11/45 computers, was introduced in 1973. First appears multiprogramming related facilities. The first commercial version is V6 and appeared in 1976.
V7 version is released in 1978 to work on the PDP 11/70 computers Interdict 8 / 2 and the 32V VAX minicomputers. Version was distributed free in U.S. universities, the source code level, which has stimulated research in operating systems and was popular UNIX system. During this period when the first events organized to standardize the UNIX system, which is not only research but also produced object. AT & T Group Company creates USG (UNIX Support Group), which assumes control and responsibility for distribution of UNIX. The first version of this group is distributed UNIX System III, which appeared in 1982.
A strong influence on the development of the UNIX system had, in addition to Bell and AT & T, University of California at Berkeley, to develop versions of BSD and BSD-3-4. These versions contain facilities for paging virtual memory management and networking facilities. It was created C-Shell user interface, have introduced new text editor (VI and EX) and compiler for Pascal and Lisp.
Free distribution of UNIX source system has led to the emergence of a large number of versions and even “disputes” between powerful groups to standardize it in one form or another. Besides version 8, System V and BSD versions can remember (some of which not only makes a UNIX-like functionality) as: ULTRIX, XENIX, AIX, VENIX, ZEUS, HP-XX, and Solaris.
One of the most used “flavor” Unix is Linux, which has a very interesting history, being an example of collaboration of thousands of strangers, united only by their passion for computers and the desire to have a good and cheap software ( free if possible). Initiator, as it were, was Finnish student Linus Torvalds. Trying to transfer some files over the network (stuff happens in 1991 when Linus bought his first PC) and realized that MSDOS’s could not help him too much so I went to work.
“I had to write a driver disk. I wrote. Then we had to devise a file system to read and write files on the central system
Minix. All operations must take place simultaneously, so we needed multitasking. But what else than UNIX is a multitasking operating system? It has its own file system and peripheral drivers. ” Thus appeared Linux kernel and enthusiasts filled him, and contributed to the development of qualified successor. Linux can be copied, modified and distributed freely. You can not put restrictions on the distribution and sources should always be available for anyone who wants to compile them or modify them. To obtain a Linux distribution (RedHat, Slackware, Debian) on magnetic media is paid not only support costs. Linux versions appear quite often, so it’s hard to be in touch with me. Those wishing to become involved in a project of documentation related to Linux can learn more about the admin page of the laboratory.
Unix system characteristics
UNIX is a general purpose operating system, multiuser, multiprocessor, system working in time-sharing. Among the attractive features that make it lists the following:
• It is an operating system with a relatively simple interface, with various utility programs covering a wide range of applications (networking, graphics, data bases yes and artificial intelligence). Available compilers and programming environments for high level programming languages (Basic, Fortran 77, Pascal, C, Lisp, Prolog)
• Unix is a multiuser system, enabling simultaneous work on several terminals DDE
• It is a portable, and can be implemented on different types of computers
• Unix is a file system directory tree with files organized simple (string of bytes) and grouped in folders.
• Unix has an input / output generalized to treat the same files, peripherals, memory and communications internal process
• Unix has a simple mechanism for memory management using the concept of virtual memory, providing a high level of multiprogramming.
• Unix has an effective system of information protection by using passwords and access rights
• Unix has a simple user interface, called SHELL, which can be extended at a high level programming language, type C, with a different kernel shell (command interpreter the user can load that you want) .
• Unix processes are reentrant (processes that have the identical code using a single copy of code, memory-resident)
UNIX System Structure
Unix operating system contains a nucleus (the residence) and a large number of software tools accessible via the command interpreter. Interface to all these utilities and user programs are done through a core set of system functions. The user has three levels of access to the system:
• by utilities;
• the standard library functions of C (intermediate level)
• system directives (low);
The core is the intermediary between the interface provided by system calls and physical facilities. Core made:
• file management;
• memory management;
• Planning processes for execution;
System calls define the programmer interface. System calls are three categories:
• Handling files (peripheral);
• control execution processes;
• Information handling;
