Week 06 Notes for CST8281 - Fall 2011

Ian! D. Allen - idallen@idallen.ca - www.idallen.com

Fall 2011 - September to December 2011 - Updated 2011-10-19 06:32 EDT

1 Midterm Test #1 - 15%Indexup to index

2 Lecture Notes for This WeekIndexup to index

2.2 From Blackboard Course DocumentsIndexup to index

These documents have restricted distribution and cannot be put on the Course Home Page.

2.3 From the InternetIndexup to index

2.4 From the Classroom Whiteboard/ChalkboardIndexup to index

2.4.1 Character EncodingIndexup to index

  • Character codes: ASCII, extended ASCII, EBCDIC, Unicode, UTF-8
    • ASCII Control Characters (unprintable)
    • line ends for text files on Unix/Mac/Windows
    • reading character tables
    • compare ASCII & EBCDIC for sort order and common printable characters
    • ASCII puts ‘A’ before ‘a’; EBCDIC does the reverse
    • tabs vs. spaces
    • know the Seven Famous ASCII Characters
      • 0D 0A 20 30 41 61 7F
    • do not memorize any EBCDIC
    • how to print the decimal value of 00001111(2) on the screen in ASCII?
      • decimal value is 15: send 31h and 35h (“1” and “5”)
  • Problems with all the 8-bit extended-ASCII character sets
    • can’t have Latin1 French and Latin2 Polish in the same text file: why?
  • UTF-8 advantages and disadvantages
    • same as ASCII, no endian-ness, multi-byte, full Unicode, may require more bytes than Unicode
  • Fonts vs. Character codes
    • codes only say what letter, not what it looks like
  • Why can’t French (Latin1) and Polish (Latin2) exist in the same text file?
    • same problem for all the 8-bit extended-ASCII character sets
  • Memory speeds (latencies) (06.ppt #7)
    • 1ns-2ns - registers
    • 3ns-10ns - Level 1 Cache
    • 25ns-50ns - Level 2 Cache
    • 30ns-90ns - main memory
    • 5ms-20ms - fixed hard disk
    • Source: 06.ppt slide 7 (under [Blackboard] Course Content - Slides)
| Ian! D. Allen  -  idallen@idallen.ca  -  Ottawa, Ontario, Canada
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