Unix Operating System

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Unix Operating System

• History
• System Architecture
• Process
• Memory
• File System

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History

• UNICS
• Uniplexed Information and Computing Service
• Bell Labs
• Portable UNIX
• Portable C compiler

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History

• Berkeley UNIX
• 4.3BSD
• Standard UNIX
• System V Release 3, 4
• POSIX
• OSF (Open Software Foundation)
• IBM, DEC, HP

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System Architecture
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System Architecture

• UNIX Kernel Functions
• Process scheduling
• Memory management
• Device management
• Disk and file management
• System call interface
• Operator console interface

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System Architecture

• Protection Rings
• User space
• Kernel space

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Process

• Definition
• The execution of an image of a virtual machine
• ps Command
• Process 0 swapper
• swapin/out, sched, swtch
• Process 1 init

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Process

• fork vs. exec
• Parent and child process
• vfork

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Process

• States and Transition

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Memory

• Physical Memory
• Virtual Memory
• Swap Memory
• Demand Paging
• Page Table

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Memory

• The UNIX Memory Model

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Memory

• Process Image

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Memory

• Demand Paging

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File System

• Directory Structure

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File System

• File Links
• hard and symbolic
• ln command
• File Permissions
• owner, group, other
• read, write, execute
• chmod command

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File System

• File Identification
• inode
• Logical Addressing
• mount command