Introduction to Algorithmic Processes CMPSC 201C Fall 2000

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Introduction to Algorithmic ProcessesCMPSC
201CFall 2000
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Administrative Issues

• Homework due Wed. 9/20 by 500 in 202 Pond.
• Exam 1 - Tuesday 9/26 at 630 - 745 PM
• Sections 1, 2, 7, 8, 11, and 12 in 111 Forum
• (Nidhi and Anand)
• Sections 3, 4, 5, 6, 9, and 10 in 102 Forum
• (John and Pyush)

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Schedule

• Mon. 9/25 No Lecture, Recitation - review
• Tues. 9/26 Exam
• Wed. 9/27 Guest lecture (you may be tested on
  material!)
• Fri. 9/29 Recitation - MATLAB
• Mon. 10/2 Lecture - Chapter 4
• Wed. 10/4 Lecture - Chapter 4
• Fri. 10/6 Recitation - MATLAB
• Mon. 10/9 No lecture of recitation.

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If you miss the exam

• You will be permitted to take a comprehensive
  make-up exam at the end of the semester if you
  bring proof of why you missed the exam.
• If you are sick, see a doctor before the exam and
  get an excuse!

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Exam

• 40 multiple choice and True/False questions worth
  5 points.
• No calculators, books, notes, etc. will be
  permitted.
• Exams will be on scantrons-- bring a pencil.
• IDs will be checked!
• Know your section number!

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Practice Exam

• Will be on I-drive and web pages by Friday 9/29.
• From Spring 2000 (the answers have not been
  checked!)
• Also read book and answer questions in chapters.

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Questions????
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Variables of type bool

• If you want a variable that is either equal to
  true or false (1 or 0), you can declare it as a
  bool type.
• Ex Suppose you were writing a program that
  sorted a list of numbers. You may use a flag
  called sorted to indicate when the list is in
  order. You perform the sort when this flag is
  false and stop when it becomes true.
• bool sorted

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Variables of type bool

• Then in the code you can set this variable equal
  to true or false using an assignment statement.
• sorted true

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Variables of type bool

• Are often used in conditions or loops.
• Ex
• while (!sorted)
• perform the sort procedure
• when some condition is met set sorted
• equal to true (sorted true)

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Problems

• Some compilers do not recognize bool data type.
  Then the line
• typedef enumfalse, true bool
• must be inserted before the declaration.

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Increment and Decrement

• Increment and decrement- i, i
• i is the same as i i1
• likewise
• i-- is the same as i i-1
• Used as a shorthand in writing code.

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Pre and Post Increment

• However you also have pre-increment and
  post-increment (i and i) as well as pre- and
  post decrement (--i and i--)
• When used alone, they are equivalent. For
  example as part of a loop
• while ( i lt somenumber)
• do something
• i

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Pre and Post Increment

• However, when used as part of an assignment
  statement, different effects occur
• a b does not give the same results as
• a b
• Suppose b 5,
• then a b would store value of 5 in a and
  change b to 6 (b b1)
• whereas a b changes b to 6 first then
  stores the value of 6 in the variable a.

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Pre and Post Increment

• a b
• is equivalent to writing two statements
• a b
• b b1
• similarly
• a b
• is equivalent to writing
• b b1
• a b

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Pre and Post Increment

• In both cases b is changed. The difference is
  when it is changed.
• a b b is modified after storing
• the value in a.
• a b b is modified before
• storing the value in a.

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Pre and Post Increment

• Although a nice shorthand for writing code, using
  the increment operator can become confusing when
  you (or someone else) tries to modify the code
  later.
• Think about this expression
• someVar a --b/c

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Test Hints

• Read code carefully! Look at what is written,
  not necessarily what you expect the code to do.
• Look for short cuts to eliminate some of the
  choices.

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