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Lesson_1.md

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Lecture 01

History of UNIX

  • UNIX was developed in 1969 at AT&T Bell Labs by Ken Thompson, Dennis Ritchie, and others.

    • Back then it was called Multics.
    • It was originally developed for the PDP-7 minicomputer.

  • The C programming language was developed by Dennis Ritchie in 1972.

    • C was originally developed for the UNIX operating system.
    • The entire UNIX operating then was rewritten in C.

  • Because of all the diverging OperatingSystems the IEEE decided to standardize the software under the POSIX standard

    • The POSIX standard is a set of standards for maintaining compatibility between operating systems.

    • POSIX is an acronym for Portable Operating System Interface (POSIX) of UNIX.

    • To be POSIX compliant, an operating system must provide a standard set of interfaces to the system's services.

  • In the wake of openly distributed Operating systems a standard set of tools was also create the GNU project

What is UNIX?

  • Operating system developed in 1969 by Ken Thompson, Dennis Ritchie and others at AT&T Bell Labs
  • Killer features:
    • Multi-user
    • Multi-tasking
    • Portable!!

Unix philosophy

  • Write programs that do one thing and do it well.
  • Write programs to work together.
  • Write programs to handle text streams, because that is a universal interface.

Unix wars and the GNU project

Unix wars

  • AT&T licensed UNIX to universities for free.
  • But AT&T was bought by Novell and they started charging for UNIX.
  • This led to the development of competing UNIX operating systems
    • First BSD (Berkeley Software Distribution)
    • Then Linux (Linus Torvalds) + GNU (Richard Stallman)3
  • Resulted in the POSIX standard (Portable Operating System Interface (POSIX) of UNIX)

GNU project

  • GNU is an acronym for GNU's Not UNIX
  • GNU is a project to create a free operating system
  • GNU is a collection of tools to make a complete operating system

Linux

  • Linux is a Kernel not an operating system.
  • Linux is a UNIX clone
  • Linux is supplied with GNU tools to make it a complete operating system
  • Developed by Linus Torvalds in 1991
  • Linux is open source

Open Source vs Free Software

Open Source

  • Developed in the 80s
  • Open source software is software that can be freely used, changed, and shared (in modified or unmodified form) by anyone.
  • Open source software is made by many people, and distributed under licenses that comply with the Open Source Definition.
  • Open source software is usually developed as a public collaboration and made freely available.
  • Can be used for commercial purposes.

Free Software

  • Developed in the 90s
  • Opens source with a political agenda
  • Free software is software that can be freely used, changed, and shared (in modified or unmodified form) by anyone.
  • Free software is made by many people, and distributed under licenses that comply with the Free Software Definition.
  • More restrictive than open source