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Operating Systems

Operating Systems. An Introduction to Operating Systems Using UNIX. What is an Operating System (OS)?. A computer program Performs many operations: Allows you to communicate with the computer (tell it what to do) Controls access (login) to the computer

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Operating Systems

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  1. Operating Systems An Introduction to Operating Systems Using UNIX

  2. What is an Operating System (OS)? • A computer program • Performs many operations: • Allows you to communicate with the computer (tell it what to do) • Controls access (login) to the computer • Keeps track of all “processes” currently running • At this point, your main concern is how to communicate with the computer using the OS

  3. How Do I Communicate With the Computer Using the OS? • You communicate using the particular OS’s • user interface • Graphical User Interface (GUI) - Windows • Command-driven interface - DOS, UNIX, • Linux • We will be using Linux, which is very similar to • UNIX

  4. How Do I Communicate With the Computer Using the OS? • When you log in to the Linux system here, a • user prompt will be displayed: • linux1[#]% _ • where # is the “number” of the command that • you are about to type • If this prompt is not on the screen at any time, • you are not communicating with the OS

  5. UNIX Overview • Files • Directories • Commands • Resources • books • links from course homepage

  6. UNIX Files • A file is a sequence of bytes • Created by text editor (emacs, pico) • Created by other programs • May contain a program, data, a document, or other information (but all are text) • Files which contain other files are called “directories” (sometimes called folders)

  7. Filenames • Restrictions • no blanks, no metacharacters, length • case sensitive • Wildcards: * ?

  8. Directories • Directories can contain files or other directories called subdirectories • Directories are organized in a hierarchical fashion • They help us to keep our files organized

  9. Directories /afs/umbc.edu/users/b/o/bob junk recipes pie cookie apple peach choc_chip

  10. Directories • Your home directory is where you are located when you log in • The current directory is where you are located at any time while you are using the system • Files within the same directory must be given unique names • paths allow us to give the same name to different files located in different directories • Each running program has a current directory and all filenames are implicitly assumed to start with the name of that directory unless they begin with a slash

  11. Subdirectories • Organizing your files • For example • make a subdirectory for CS104 • make subdirectories for each project

  12. Moving in the Directory Tree • . (dot) is the current directory • . . (dot-dot) is the parent directory • UNIX command cd “change directory” • Use dot-dot to move up the tree • Use directory name to move down • Use complete directory name (path name) to move anywhere

  13. Commands • cp, mv, ls, rm, more, cat, cd, pwd • mkdir, rmdir, passwd, man, lpr • redirection: | < > • ctl-c, ctl-d

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