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Session 22 – March 31, 2003
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AGENDA:
0 Admin
1 VSP V.2
2 Ch 5.1: files
3 Ch 5.2: directories

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0 – ADMIN
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Startout Q: What did you learn from VSP V.1?

Due Wednesday
* RI #7, covers Ch 5.1-5

Due Friday
* HM #5: Questions 5.3, 5.6, 5.7, 5.10, and 5.14.

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1 – VSP V.2 DISCUSSION
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What did you learn from VSP V.1?








What are your thoughts for V.2?





How about having both a block & serial device
  interface?

What are the design considerations?
* universal read, authenticated write
* how to handle the semantics of multiple writers
* UDP vs. TCP



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2 – CH 5.1 FILES
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So you want to design a file system.
What do you need to think about.
* Discussion

Things to think about
* file naming
  - case, length, extensions
* internal file structure
  - byte stream, fixed size records, DB tree
* file types
  - regular files, directories, block and char. dev.,
    binary vs. ASCII, bin. formats (fig 5-3 p. 406)
* file access
  - sequential vs. random/arbitrary
    sequential may be read only sequentially, may be
      rewound to beginning of file
  - random provides a seek() function for positioning
* file attributes
  - protection, password, creator, owner, read-only,
    hidden, system, archive, ASCII/binary, random
    access, temporary, lock, record length, key pos
    w/in record, key length, creation time, last
    access, last change, size, max_size, append-only,
    etc.
  - multiple file data streams, eg. Mac & NT
* file operations
  - create, delete, open, close, read, write, append,
    seek, get attributes, set attributes, rename

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3 – CH 5.2 DIRECTORIES
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What is a directory?
Where do you store the file attributes?
* in dir, elsewhere, some combo.
* multiple file systems
  fig 5-6 p. 412
* path names
  - absolute vs. relative
  - working directory
  - '.' and '..' in UNIX/DOS/etc.
Directory operations
* create, delete
* open, close, read
  opendir, closedir, readdir
* rename, link, unlink


COS 421 – Lecture Notes #22		SPRING 2003	
COS421-lect-2003-03-31	Page 1	Printed 31.03.03