Introduction to UNIX.


  1. What is UNIX?

    UNIX is a mature family of operating systems with a proven track record for performance, reliability, and security in a server environment. UNIX is a multiuser, multitasking operating system where processes compete for systems resources. UNIX is a scalable OS (operating system) that runs on various computer hardware platforms from PCs to large supercomputers.
    1. Multiuser A computer system that can be used by more than one person at a time.
    2. Multitasking A computer system that allows a user to run more than one job at a time.

  2. UNIX Anatomy.

    UNIX is built on open standards, the basic anatomy of the UNIX system is:

  3. The History of UNIX.


    1965
    Bell Labs, MIT and General Electric work on the Multics operating system project (Multiplexed Information and Computing Service). The goal of Multics was to provide a multi-user, multi-processor and hierarchical file system.

    1969
    The first version of UNIX was written for a PDP-7. The name UNIX (UNICS) is a pun on a prior OS MULTICS. MULTICS attempted to solve many problems. UNIX tried to do one thing well - To provide for a program development workbench. The basic file system, the shell and other characteristics come directly from MULTICS.

    1970
    UNIX is rewritten for a PDP-11. Much of the terse command syntax comes from these early systems where the memory was limited and the primary input was a Teletype. January 1, 1970 is regarded as the birthday of UNIX. All system clocks run from this time and date.

    1973
    UNIX kernel is re-written in C. The prevailing belief at that time was that an OS had to be written in assembly language to provide reasonable efficiency and to get access to the hardware. Each new hardware platform would require a complete rewrite of the OS. By implementing the OS in a high level language about 90% of the code could be ported to a new system with a compiler. Although the success of UNIX does not stem solely from the fact that is was written in a high-level language, the use of C was a critical first step.

    1974
    AT&T licensed UNIX to Universities and released the source code. This allowed Universities not only the ability to use the code, but also to tinker with it.

    1977
    There are about 500 UNIX sites worldwide.

    1978
    AT&T releases the Seventh Edition of UNIX. This was the first edition with portability as a stated goal.

    1979
    Berkeley releases UNIX 3BSD, with virtual memory, demand paging and page replacement.
    • Virtual Memory
      Programs are divided into smaller portions called pages. Under the control of the OS only the necessary pages of a program are paged into main memory to support the on-going process. This allows the system to use large programs with minimal memory demands. It makes the system appear to have more memory at the expense of processing cycles.


    1980
    Berkeley releases 4BSD with support for TCP. This will give birth to the Internet. Microsoft licenses UNIX from Bell Labs and introduces XENIX.

    1981
    IBM enters the personal computer market, creating a de facto standard.

    1983
    AT&T releases UNIX System V. After the court ordered break up of AT&T, Bell Labs starts to aggressively market System V.

    1988
    AT&T announces plans to acquire 20% of Sun Microsystems, and that Sun will help AT&T develop the next version of UNIX. In response to the AT&T - Sun cooperation, IBM, DEC, Apollo and several other major companies form the Open Software Foundation to set a UNIX standard.

    1991
    SunSoft a Sun subsidiary, announces Solaris a UNIX system for SPARC workstations and 386/486 PCs.
    Linus Torvalds released the first version of LINUX.

    1992
    Novell acquires UNIX systems laboratory from AT & T for $350 million.

    1993
    Novell transfers the UNIX trademark to X/OPEN which will certify that an OS is UNIX compliant.
    There are an estimated 3 million UNIX systems in operation.

    1996
    Linux is certified as POSIX compliant. Estimated 12 million Linux users worldwide.

    2000
    UNIX Turns 30.
    Much of the progress of computer hardware, software and networks during the last quarter century can be traced to the influence the UNIX system had on the computer industry. It embodies visionary ideas -- deliberate generality and openness -- that continue to be a strong force today. Many of its approaches and notations have influenced the entire span of subsequent operating systems.
    UNIX is the operating system of most large Internet servers, businesses and universities, and a major part of academic and industrial research in operating systems is based on UNIX. .
    "Thirty years after its creation, UNIX still remains a phenomenon," Ritchie marveled.

  4. The UNIX Family Tree.

  5. Implementations of UNIX.
© Allan Kochis Last revision 8/28/2003