5.2 Week 2 - Labor Day Week

• Questions:
  • Supercomputer word lengths - Usually 64 bits.
  • about X, X11, X window system
    A Network Protocol based Graphical User Interface that is platform independent. The server - or the display can be running on one system, the application on another, and the window manager on yet another. Servers - or displays - run on PC, Mac, & UNIX systems. Written at MIT.
  • SMP Symmetric Multi-processing. Running multiple processors with the same memory space and I/O. A low cost way of getting more computation done with lower cost hardware. Processor speeds (seem) to have a limit. It (should) (might) be easier to have multiple processors than to speed up processors at some point.
  • UNIX kernel
  • initialization
  • daemon processes.
• Status of system. Still not available by TCP/IP
• Shells. Like DOS command.com UNIX has multiple shells. Each provides a different syntax and command language to the user.
  • tcsh - the shell you will start with on X2 this semester. The "T" seems to be from the TOPS-20 DEC OS!
  • sh - Bourne shell (The "first" shell.)
  • ksh - Korn shell, used by AIX
  • bash - FSF sh follow on.
  • csh - "C" shell. C language like syntax. Arithmetic.
  • rsh - restricted shells. Limits user access.
• UNIX Command Line Interface.

  Prompt from system. User enters and edits command. No action until carriage-return. System then acts on command.

  Command of the form: command-name arguments.

  Arguments can be options, file names, and/or arguments. Most options start with a hyphen. This is a convention, not a requirement.

• File Names. Depend on file system. A single system can have multiple file system types - at the same time. System V limits to 14 char. BSD can deal with 255 char file names. Few actual restrictions on file names. No nulls, no /. Spaces, Tabs, periods, and control codes all work. Just DON'T do it! Multiple dots or periods OK too.
• Arguments to commands. Most start with a hyphen. Not a requirement. Command line syntax is done by each command.
• tcsh is an enhanced but completely compatible version of the Berkeley UNIX C shell, csh(1).

  The T in tcsh. "The creator of tcsh was impressed by this feature and several others of TENEX and TOPS-20, and created a version of csh which mimicked them." The "rest" of the story is in the tcsh manual pages.

  It has file name, user name, and command name completion. It can (and does) remember across login/logout boundary. Name completion even works when you are using history. File name completion uses the tab key.