Download 1Lecture.OS

Operating Systems
• An integrated collection of utilities…
• …that manage the operations of the
hardware and maintain information storage
and retrieval
• OS contains the “rules” of machine
operation…
• …based on the architecture of the processor
(CISC (pentium, power-pc), RISC (alpha, sparc, 680x0)
• Components (must be resident in memory):
– Supervisor = monitor, controlling unit
• Coordinates all activities of the OS
• Activates utilities as needed for functionality
– Utilities = collection of sub-programs
• I/O handling, user interface, scheduling, interrupt
handling, memory management, program
loading/unloading, foreground/background control,
compression, paging, status…
Tree structures
• Multi-user operating system
• (UNIX)
• Single-user operating system
• (DOS)
• (Windows) GUI representation of a
“network-aware” environment
Multi-user structure (UNIX)
• User sees a subset of the file structure
• Administrator must protect the system files
• User must protect own files (file rights)
_____________ / [root]___________________________________
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|
|
|
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/bin
/home
/usr
/etc
/unix
|--|--|--|--|--|--| |--|--|--|
|---|-|
|---|---|
|---|---|
cat vi who ls
/a …/z
/bin
passwd
|----------|-----------|
/acmt0001 /andj0001 …/others…[home – “root” to user]
|
|
/homepage /homepage
index.html
index.html
Single-user structure (DOS)
• View only one logical drive at a time
• Logical drive represents the root
• System files are accessible to user
C: \ [root of logical drive]
|
| -DOS
|
-FORMAT.COM
|
-XCOPY.EXE
| -MYFILES
|
-MYDOC.DOC
| AUTOEXEC.BAT
| CONFIG.SYS
| COMMAND.COM
GUI representation (Windows)
• Combines DOS structure with a global view
• Includes hardware and logical world
Desktop [user centric view of the world]
| -MyComputer [computer centric view]
| | +A:\ [root of logical drive] (floppy)
| | +C:\ [root of logical drive]
| |
-DOS
| |
-Windows
| | +D:\ [root of logical drive]
| | +E: \[root of logical drive] (CD-ROM)
| | -[printers]
| | -[control panel]
| | -[web pages]
|-Network Neighborhood [peers]
|-recycle bin
|-myBriefcase
UNIX file rights - chmod
• Set rights for: ugo (user, group, others)
• Set access: rwx (read, write, execute)
– home directory by default = drwxr-xr-x
– remove read/write/exec for group and others
chmod go-rwx
– make sure web pages are visible in /homepage
chmod go+rx homepage