Academic Misconduct InputOutput Conditionals Writing a Simple Algorithm

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Academic MisconductInput/OutputConditionalsWrit
ing a Simple Algorithm
Lecture 3
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Who are these people and why are they looking at
me?
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Academic Misconduct
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From the syllabus...

• All assignments must reflect an individual
  effort, and must be completed "from scratch". It
  is a violation of the honor code to copy or
  derive solutions from textbooks, internet
  resources or previous instances of this course.
  Copying of solutions from other students,
  including those who previously took the course is
  prohibited. A good guideline is that you must be
  able to explain and/or reproduce anything that
  you submit.

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Dear CS1311 Students,

• Be forewarned about the consequences of cheating
  in CS 1311, and give them serious thought. In the
  end your costs strongly outweigh your benefits.
  Even though the class can be confusing and
  sometimes even overwhelming, you must not let
  your frustration get the best of you. When and if
  you are still unsure just turn in what you have,
  dont take the risk of copying someone elses
  work. Taking the attitude that you are
  invincible and that you will never get caught
  could land you in the Deans office at the end of
  the quarter. So dont take the cheat finder
  lightly because it really does exist (for
  homework and lab projects!) Unfortunately, as a
  former CS 1311 student, I can personally assure
  that if you are going to cheat you are going to
  pay a heavy toll for it. Smart people learn from
  their own mistakes, geniuses learn from others
  mistakes.
• Sincerely,
• Anonymous CS 1311 Student

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What is cheating?

• Cheating is gaining an unfair advantage over
  others and/or misrepresenting yourself on your
  work for academic gain.
• The intent to cheat is not a prerequisite for
  cheating to occur.

Its not worth it!
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Consequences

• F in the course is probable
• University probation
• Mandatory participation in community service
  hours
• Loss of Hope Scholarship or any other scholarship
• Lowered GPA- with possible probation or even
  expulsion from the university
• Loss of job opportunities
• Possible ineligibility for the co-op program

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Questions?
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Input and Output
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Input and Output

• I/O Operators allow us to communicate with the
  outside world, the world beyond the algorithm
  itself.
• Were not concerned with formatting.

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Print

• Displays output items to the user
• Syntax
• print(item_1, item_2, ..., item_n)
• Examples
• print(Please enter your info.)
• print(num_one, my_char, is_Student)

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Read

• Obtains input items from the user
• Syntax
• read(item_1, item_2, ..., item_n)
• Examples
• read(menu_choice)
• read(is_Student, name, age)
• No automatic prompting!

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Input and Output Examples

• algorithm IO_Example
• num_one, num_two, average isoftype Num
• // obtain two numbers
• print(Please enter two numbers)
• read (num_one, num_two)
• // output a literal text message and the
• // value of the sum
• print (Sum , num_one num_two)
• // output a string literal and average
• average lt- (num_one num_two) / 2
• print (Average , average)
• endalgorithm

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ESP Formatting
LB

• Conventional languages require you to learn
  complex, intricate and often tricky formatting
  techniques.
• With pseudocode the situation is much simpler
• All tricky formatting manipulations are
  accomplished by just thinking about it and it
  happens
• Leading edge pseudocode...
• ...its whats for dinner.

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Questions?
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Conditionals
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Relational Operators

• Greater than gt
• Greater or equal gt
• Equal to
• Less than or equal lt
• Less than lt
• Not equal to lt gt

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Using Relational Operators

• Combining relation operators with operands
  generates a boolean value
• Examples
• 4 gt 5 FALSE
• apple lt cat TRUE (alphabetic)
• 5 ltgt 6 TRUE
• 42 42 TRUE
• g gt x FALSE

LB
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Boolean Operators

• Boolean operators allow us to express compound
  expressions.
• AND
• OR
• NOT

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AND

• AND - all conditions must be true
• ((5gt4) AND (4gt7)) is FALSE
• TRUE FALSE

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OR

• OR - only one condition must be true
• ((5gt4) OR (4gt7)) is TRUE
• TRUE FALSE

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NOT

• NOT - reverses the boolean value
• NOT (4gt7) is TRUE
• FALSE

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Boolean Expressions

• Boolean expressions evaluate to TRUE or FALSE and
  are composed of
• boolean variables(is_too_young) // a boolean
• expressions with relational operator(10 lt y)
• - expression with logical operators
• ((10 gt x) AND (x lt 20)) OR (y -4)
• (0 lt age lt 20) is not legal and should be written
  ((0 lt age) AND (age lt 20)).

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Naming Boolean Variables
LB

• Names should be chosen to make clear what the
  true or false value represents

• Bad Examples
• red_or_green
• gender
• pass_fail
• on_off

• Good Examples
• is_red
• is_male
• did_pass
• is_on

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Decision Statements

• Conditionals allow us to make decisions based
  upon simple logic. Results of conditionals are
  always TRUE or FALSE, i.e., boolean values.
• Natural Language
• The number of hours is greater than or equal to
  15.
• Picture
• num_of_hours gt 15
• Code
• if (num_of_hours gt 15) then...

TRUE
FALSE
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Simple Conditionals

• Allows for some instructions to be conditionally
  executed.
• Basic template
• if ( BOOLEAN_EXPRESSION ) then
• any instructions
• endif

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If-Then-Endif

• if ( BOOLEAN_EXPRESSION ) then
• any instructions
• endif
• If the BOOLEAN_EXPRESSION is TRUE, then execute
  all of the instructions in the then clause and
  continue the algorithm.
• If the BOOLEAN_EXPRESSION is FALSE, then skip to
  the endif and continue the algorithm.

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If-Then-Endif Example

• wake up
• if ( is_raining ) then
• stay inside and play board games
• go to see a movie
• read a book
• call friends
• endif
• go to sleep

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If-Then-Else-Endif

• if ( BOOLEAN_EXPRESSION ) then
• any instructions to execute if true
• else
• any instructions to execute if false
• endif
• If the BOOLEAN_EXPRESSION is TRUE, then execute
  all of the instructions in the then clause until
  you reach else, then skip down to the endif and
  continue the algorithm.
• If the BOOLEAN_EXPRESSION is FALSE, then execute
  all of the instructions in the else clause and
  continue the algorithm.
• Cannot do both the if clause and the else clause
  only one or the other.

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If-Then-Else-Endif Example

• if ( is_raining ) then
• stay inside and read a book
• go to see a movie
• else
• go to the park
• go swimming
• endif
• go to sleep

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Nested Conditionals
Conditionals can reside inside other conditionals

• if (today Sunday) then
• if (NOT raining) then
• go to the park
• else
• stay home read a book
• endif
• else
• go to work
• endif

Use indenting to make the code clear!
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The Optional Elseif Clause

• Often we want a way to select one from many
• if (grade gt 90) then
• print(You get an A)
• elseif (grade gt 80) then
• print(You get a B)
• elseif (grade gt 70) then
• print(You get a C)
• elseif (grade gt 60) then
• print(You get a D)
• else // the default
• print(Sorry, you get an F)
• endif

Why not gradegt 80 AND lt 90 ?
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A Complex Conditional

• if (withdrew_from_course TRUE) then
• print(Sorry to see you leave)
• elseif (((quiz_grade gt 60) or
• (final_exam gt 60)) and
• (did_homework)) then
• print(You pass the course)
• else
• print(Sorry, see you next term)
• endif

See anything redundant?
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A Complex Conditional

• if (withdrew_from_course) then
• print(Sorry to see you leave)
• elseif (((quiz_grade gt 60) or
• (final_exam gt 60)) and
• (did_homework)) then
• print(You pass the course)
• else
• print(Sorry, see you next term)
• endif

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Questions?
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Writing Algorithms
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Recipe for Writing Algorithms

• Write the shell
• Outline the logic
• Code the main ideas
• Verify declarations
• Verify constants
• Walk through the code
• - syntax errors
• - logic errors

Note that you still have work to do after youve
finished writing the code!
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Writing a Simple Algorithm
algorithm // constants // declarations //
program endalgorithm
Get_Circumference //
Get_Cirumference
PI is 3.14159265

• Write the shell

radius isoftype Num diameter isoftype Num circumf
isoftype Num
3

• Name the algorithm

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18.85

• Outline the logic

• Fill in the algorithm

// Get the data // Compute circumference //
Output the answer

• Declare the variables

print(Enter the radius) read( radius )

• Define the constants

• Walk the code

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Enter the radius
diameter lt- radius 2 circumf lt- diameter PI
Diameter is 6
Circumference is 18.85
print(Diameter is , diameter) print(Circumfere
nce is , circumf )
Done!
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Questions?
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