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History OS UNIX UI Security Questions UNIX-like Operating Systems by Roman Szturc Simple, Low-Power Machines History OS UNIX UI Security Questions user had sole use of the machine, program was loaded into the machine and the machine set to work, task is responsible for everything, task totaly determines behavior of computer. machines came with libraries of support code which were linked to the user’s program to assist in operations such as input and output This would become the genesis of the modern-day operating system. More Powerful Computers History OS Later, more powerful computers appeared. They were characterized as follows: UNIX UI CPU is much faster than R/W operations, Security CPU is idle while R/W operation in progress, Questions CPU can perform other task while idle. Need to manage multiple tasks Task switching. Task scheduling. Operating System History OS UNIX UI An operating system (OS) is the system (low-level) software responsible for Security Questions direct control and management of hardware, task management, storage allocation, presentation of a default user interface. Program and Process process2 History data2 OS UNIX UI Security process1 Questions data1 PSfrag replacements program code memory Early Operating Systems History OS Early OS had some problems. The OS UNIX UI Security Questions were very diverse — each OS specific to particular hardware, used radically different models of commands and procedures, Typically, each time the manufacturer brought out a new machine, there would be a new OS. UNIX History UNIX is an OS developed in the 1960s and 1970s by AT&T Bell Labs employees including K. Thompson, D. Ritchie, and D. McIlroy. It was designed to be OS UNIX UI Security Questions portable, multi-tasking and multi-user. The UNIX systems are characterized by various concepts: plain text files, command line interpreter, hierarchical file system, treating devices and certain types of inter-process communication as files. Unix Architecture History OS UNIX UI Security Questions PSfrag replacements shell utilities kernel hardware Unix-like systems History OS UNIX UI Security Questions UNIX Philosophy There are the following ideas characterizing the UNIX philosophy: History OS UNIX UI Security Questions write simple parts connected by clean interfaces. clarity is better than cleverness, design programs to be connected to other programs, separate policy from mechanism; separate interfaces from engines, when a program has nothing surprising to say, it should say nothing, when you must fail, fail noisily and as soon as possible, design for the future, because it will be here sooner than you think. File System History OS UNIX UI Every item in a UNIX file system can de defined as belonging to one of four possible types: Security Questions ordinary file, directory, special file, links. Pipe History OS UNIX UI Security A pipe “|” sends data from standard output of source process to standard input of destination process. if [ $(wget -O - http://www.vltava.cz/... | grep -c "Perl") -gt 0 ]; then mail -s "Book" [email protected] << EOF Questions You can order the Perl book at vltava.cz. Your book notifier . EOF fi User Interfaces History OS UNIX UI Security Questions One of the most heated and ancient battles is over the choice of Graphical User Interface (GUI) vs. Command Line Interface (CLI). Advantages of CLI structure of UNIX and of its shells allows powerful mechanisms of piping and redirection, porting CLI utility to other system is relatively easy task, CLI utilities incur much less size and speed overhead than their graphical counterparts, textual information is also much smaller than graphical, obviously making remote connections less of a pain in the neck. User Interfaces (continued) History OS UNIX UI Security Questions Advantages of GUI prettier and more natural feel, modern computing is very much focused on media and that is naturally only done with graphical environments, graphical desktop allows true multitasking (for the user) to take place, an important benefit is the display of dynamically modifiable abstract information — one click can replace several commands. User Interfaces (continued) Learning Curve History OS UNIX ability to use an OS UI Security Questions PSfrag replacements CLI GUI time X Window System X display (Windows) X screen Solaris History X server X client OS UNIX net UI Security Questions AIX ag replacements X client X display (Linux) X server X client X screen X screen X client Window Managers and Desktops History OS UNIX UI Security Questions Window Manager A window manager is software that controls the placement and appearance of application windows under the X Window System. The most popular ones are: AfterStep, Enlightenment, WindowMaker, Metacity, TWM, Kwin, MWM, FWM, IceWM, Sawfish, . . . Desktop A desktop consists of what is on the screen before any windows are opened, and what reappears when windows are closed. It usually shows icons for programs, documents or folders and possibly an image as wallpaper. The most popular ones are: GNOME, KDE, XFCE, CDE. Security History OS Security is inherent part of multiuser OS. It grants privacy of user data OS stability. UNIX UI Security Questions Authentication is process by which a computer attempts to ensure that users are who they say they are. Authorization is a process that protects computer resources by only allowing those resources to be used by resource consumers that have been granted authority to use them. UNIX Distributions History OS Over the years there were more than 250 versions of UNIX-like systems released. The following are the most significant ones: UNIX UI Security Questions (Net,Free,Open)BSD Darwin Mac OS X (Open)Solaris Linux z/OS Unix V1R7 AIX IRIX Leading Areas History OS UNIX UI Internet backbone, Security multiprocessor systems, Questions critical applications, need of extremely high up-time, Questions History OS UNIX There are several frequently asked questions concerning UNIX systems. UI Security Questions UNIX is more than 30 years-old. Is it worth to linger with such an antique? Is UNIX dangerous? Why should I type a complicated commands instead of select menu items? Why UNIX disallows users to do mistakes?