Academic MisconductInput/OutputConditionals

Writing a Simple Algorithm

Who are these people and why

are they looking at me?

Academic Misconduct

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.

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, don’t take the risk of copying someone else’s work. Taking the attitude that you are invincible and that you will never get caught could land you in the Dean’s office at the end of the quarter. So don’t 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 other’s mistakes.”

Sincerely,

Anonymous CS 1311 Student

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.

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

Questions?

Input and Output

Input and Output

I/O Operators allow us to communicate with the “outside world,” the world beyond the algorithm itself.

We’re not concerned with formatting.

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)

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!

Input and Output Examplesalgorithm 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 <- (num_one + num_two) / 2 print (“Average = “, average)endalgorithm

ESP Formatting

• 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...

...it’s what’s for dinner.

LB

Questions?

Conditionals

Relational Operators

• Greater than >• Greater or equal >=• Equal to =• Less than or equal <=• Less than <• Not equal to < >

Using Relational Operators

Combining relation operators with operands generates a boolean value

Examples:

4 > 5 FALSE

“apple” <= “cat” TRUE (alphabetic)

5 <> 6 TRUE

42 = 42 TRUE

‘g’ > ‘x’ FALSE LB

Boolean Operators

Boolean operators allow us to express compound expressions.

– AND

– OR

– NOT

<Boolean Value> <Boolean Operator> <Boolean Value>

LB

AND

AND - all conditions must be true

((5>4) AND (4>7)) is FALSE TRUE FALSE

AND F T

F F F

T F T

In use there wouldbe some variables!

OR

OR - only one condition must be true

((5>4) OR (4>7)) is TRUE TRUE FALSE

OR F T

F F T

T T T

NOT

• NOT - reverses the boolean value

NOT (4>7) is TRUE FALSE

NOT

F T

T F

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 < y)

- expression with logical operators((10 >= x) AND (x < 20)) OR (y = -4)

(0 < age < 20) is not legal and should be written ((0 < age) AND (age < 20)).

LB

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

Naming Boolean Variables

• Bad Examples

red_or_green

gender

pass_fail

on_off

• Good Examples

is_red

is_male

did_pass

is_on

Decision StatementsConditionals 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 >= 15

Code:

if (num_of_hours >= 15) then...

TRUE

FALSE

Simple Conditionals

Allows for some instructions to be conditionally executed.

Basic template:

if ( BOOLEAN_EXPRESSION ) then any instructionsendif

If-Then-Endif

if ( BOOLEAN_EXPRESSION ) then any instructionsendif

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.

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 friendsendif

go to sleep

If-Then-Else-Endif

if ( BOOLEAN_EXPRESSION ) then any instructions to execute if trueelse any instructions to execute if falseendif

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.

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

Nested Conditionals

if (today = Sunday) then if (NOT raining) then go to the park else stay home & read a book endifelse go to workendif

Conditionals can reside inside other conditionals:

The Optional Elseif Clause

Often we want a way to select one from many:

if (grade >= 90) then print(“You get an ‘A’”)elseif (grade >= 80) then print(“You get a ‘B’”)elseif (grade >= 70) then print(“You get a ‘C’”)elseif (grade >= 60) then print(“You get a ‘D’”)else // the default print(“Sorry, you get an ‘F’”)endif

Why not:grade>= 80 AND < 90

?

A Complex Conditional

if (withdrew_from_course = TRUE) then

print(“Sorry to see you leave”)

elseif (((quiz_grade >= 60) or

(final_exam >= 60)) and

(did_homework)) then

print(“You pass the course”)

else

print(“Sorry, see you next term”)

endif

A Complex Conditional

if (withdrew_from_course) then

print(“Sorry to see you leave”)

elseif (((quiz_grade >= 60) or

(final_exam >= 60)) and

(did_homework)) then

print(“You pass the course”)

else

print(“Sorry, see you next term”)

endif

Questions?

Writing Algorithms

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 doafter you’ve finished writing the code!

radius isoftype Numdiameter isoftype Numcircumf isoftype Num

print(“Diameter is: “, diameter)print(“Circumference is: “, circumf )

Writing a Simple Algorithm

algorithm// constants

// declarations

// program

endalgorithm

• Write the shell

Get_Circumference

// Get_Cirumference

• Name the algorithm

// Get the data

// Compute circumference

// Output the answer

• Outline the logic

• Fill in the algorithm

print(“Enter the radius”)read( radius )

• Declare the variables

• Define the constants

PI is 3.14159265

• Walk the code:

Enter the radius:

= 3= 6

= 18.85

Diameter is: 6Circumference is: 18.85

3diameter <- radius * 2circumf <- diameter * PI

Done!

Questions?