UNIVERSITY OF TEXAS AT DALLAS COMPUTER SCIENCE DEPARTMENT

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UNIVERSITY OF TEXAS AT DALLAS COMPUTER SCIENCE
DEPARTMENT

• CS5375. Principles of Unix.
• Professor Rafael Lacambra
• http//www.utdallas.edu/Rafael.Lacambra/cs5375

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• Hardware/Software.
• UNIX Operating system
• Sharing resources
• Communications
• Utilities
• Programmer Support
• Standards

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Hardware

• Examples of input devices
• Mouse
• Keyboard
• Touchscreen
• Reading information from disk
• Scanner
• Tablet and pen
• Joystick
• Network/Modem

• Examples of output devices
• Monitor/terminal
• Printer/Plotter
• Writing information to disk
• Network/Modem
• Projector

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Software

• There are two general categories of software
  Operating System and Application Software.
• OS manages all system resources to get the best
  performance from computers. It is a program
  loaded in RAM at boot time.
• AS perform general operations word processing,
  databases, packages, utilities, commands, games...

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Applications
Shell
Utilities
UNIX Kernel
Hardware
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Software

• Single User OS allows only one user to operate
  the computer at a time. (i.e. MS-DOS)
• Multiple User OS allows several users to run
  programs and operate the computer at the same
  time. Many people can use the system resources
  almost simultaneously.

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• A file contains the source code
• A program is an executable file.
• A process is an instance of a program in
  execution.
• A job is a collection of processes

program
ex1.ca.out
ex1.c
Source file
Compile
RAM
a.out
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• Many processes can execute simultaneously on a
  UNIX system.
• Many instances of a program can exist
  simultaneously in the system.

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RAM
weather
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Kernel
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• Multitasking or multiprogramming each user on
  the system can run more than one job at the same
  time.

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RAM
weather
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Kernel
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• Multiprocessor, a computer that has more than one
  CPU. A job can be executed on one or more CPUs,
  and each CPU can do multitasking (thanks to UNIX)

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RAM
weather
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cal
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Input/Output

• Many processes read and write data from/to files.

cache
disk
RAM
weather
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Kernel of the Unix OS

• Controls the resources of the computer and
  allocates resources among users.
• Allows easy and fast access to the users' files
  by providing a filesystem that manages the
  storage of information.
• Controls all devices (disks, terminals, printers,
  etc)
• Provides security and protection.

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Kernel of the Unix OS
Manages Memory
Manages processes
Maintains Filesystems
Controls Access to Computer (users'
accounts, Permissions,)
Provides A simple user interface which offers a
set of services
Distributes System Resources
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Sharing resources

• CPUs among processes
• dividing each second of CPU time into equal-size
  slices.
• Allocates the slices based on a priority queue.
• High priority process allocates more slices.

Kernelprocess table
RAM
weather
vi
vi
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Sharing resources

• Memory among processes
• dividing RAM up into equal-size pages of memory
  
• allocating the pages based in a priority scheme.
• Only those portions of a process that actually
  need to be in RAM are ever loaded from disk.

RAM
Kernel
weather
vi
vi
pg. 6
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Sharing resources

• Unix shares disk space among users by dividing
  the disk into thousands of equal-size blocks
  and then allocating the blocks to users based on
  a quota system.
• A single file is built out of one or more blocks.
• Blocks do not have to be contiguous.

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Communication

• Process - graphics card
• Hardware control
• Process - keyboard
• Hardware control
• Process - network (mail, ftp, )
• using sockets
• Process - process
• using pipes

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Utilities

• Standard Unix has more than 200 utilities
• Editors
• C compiler
• Sorting utility
• Graphical User Interface
• Shells
• and more

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Programmer support

• Open system
• C library (systems calls) to communicate with the
  Kernel and use UNIX advantages like parallel
  programming, inter-process communication,
  sockets, etc.

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Standards

• ATT System V
• Sun Microsystems System V Release 4
• Berkeley Standard Distribution BSD
• Open Software foundation headed by HP, IBM and
  DEC create OSF

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History
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History
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• Today Unix follows ATT System V with BSD
  extensions.
• Solaris Sun Microsystems
• Irix Silicon Graphics (SGI)
• AIX IBM
• HP-UX . HP
• Or BSD
• MacOS X 10.x. Apple
• Linux (most flavors)
• True64 UNIX . Compaq
• Unicos. Cray Research
• SunOS Sun Microsystems