session     topic                            readings
=========================================================
2           Intro to computers - 1           COM1-COM17
3           Intro to computers - 2           COM17-COM30
=========================================================

- what is a computer

  - 4 components:  input, output, processor, storage

  - comprised of software and hardware

    hardware: electronic devices and media

      input: keyboard, mouse, scanner, video camera,
              microphone, etc.

      output: display, printer, plotter, videotape, audio
               tape, etc.

      storage: hard disk, floppy disk, CD-ROM, cards, tape,   
                etc.



    software: programs

      operating system:

             - boots system
             - mediates between hardware and software
             - provides file structure and file mgmt. utilities
             - provides user interface          

      applications and utilities:

             - word processors	
             - spreadsheets
             - database management systems
             - electronic mail
             - gopher/www browser
             - etc.


- talk briefly about the 'How to purchase a computer system'
    part and mention MOC

   - also very briefly mention 'How to INstall a Computer
       System'


- files and file structures

   - bits, bytes, K, M, G, T, etc.

   - a file is a set of bits

      - files are saved on STORAGE MEDIA (disks, tapes, etc.)
         by use of STORAGE DEVICES (disk drives, etc.)

      - all files are either PROGRAMS or DATA

         - programs are executed by the processor

         - DATA are interpreted into something useful
            by some program

            - DATA files can be either

               - ASCII text

               - binary (not ASCII text)   

            - mention and give examples of why the ascii/binary
               distinction is important

                - a special application program called an 
                   ASCII text editor is used to create and modify
                   ASCII text files


- some storage devices are 'directory devices'      
  
   - they maintain a directory of files, using 'file names' to
      identify and locate files

   - file structures can be flat or hierarchical

      - flat means that the storage device just contains files

      - hierarchical means the storage device can contain files 
          'subdirectories' 

          - subdirectories can contain files and more
              subdirectories

- example of storage media -- winchester disk

   - formatted into sectors and tracks

      - each has a physical address

   - formatting also creates special directory file

     - this file contains file name and  other important info
         as well as pointer to first sector/track of file

   - each sector/track ends with either pointer to next
       sector/track of file or special <EOF> character

   - operating system software writes file as 'chunks' of
      bits/bytes onto magnetic media as +/- charges that store
      the on/off binary digits.

      - the magnetic media rotates under the read/write head
        of the disk device