Flow chart and Algorithm

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Flow chart and Algorithm
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Announcement

• Exam One
• Wednesday October 1st
• 100 points
• Mixture of short answer, problem solving,
  matching, and maybe a multiple choice question
• Monday class will be held as a review session.

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Exam Next Wednesday

• History of Computers
• Hardware inside and outside
• Software Microsoft Word, Excel
• Spread sheet and data
• Operating Systems and Computer Security
• Pirates of Silicon Valley
• Writing Lab Reports
• Binary Mathematics
• Flowcharts and Algorithms

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Todays Topics

• Algorithms
• Flowcharts
• Pseudo code

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Problem Solving

• For the rest of the semester, we will practice
  problem-solving. If you learn nothing else from
  this class, I would like you to learn to take a
  good approach to problem solving

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Algorithms

• To solve a problem, you got to figure out how to
  solve it by yourself.
• To make a computer solve a problem, you need to
  you have to tell the computer, step by step,
  exactly what you want it to do.
• The computer then "executes" the program,
  following each step mechanically, to accomplish
  the end goal.
• Algorithm Sequence of step-by-step instructions
  that will produce a solution to a problem

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Four algorithms

• The taxi algorithm
• Go to the taxi stand.
• Get in a taxi.
• Give the driver my address.
• The call-me algorithm
• When your plane arrives, call my cell phone.
• Meet me outside baggage claim.

• The rent-a-car algorithm
• Take the shuttle to the rental car place.
• Rent a car.
• Follow the directions to get to my house.
• The bus algorithm
• Outside baggage claim, catch bus number 70.
• Transfer to bus 14 on Main Street.
• Get off on Grand River Ave.
• Walk two blocks north to my house.

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Problem to Solve

• What steps would you propose to solve the
  following problem?
• You are dirty and want to clean up
• Solution Take a shower
• What are the steps?

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Example of Algorithm
Take a Shower Algorithm
Problem You are dirty Solution Take a
shower How Take a Shower Algorithm

• Take clothes off
• Turn on water
• Step into shower
• Wash face
• Wash body
• Shampoo hair
• Turn water off
• Dry off
• Get dressed

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Sequence of Steps

• Fairly regular order of events
• must take clothes off first
• cannot dry off before washing
• Cannot skip steps to complete job
• Result oriented
• Termination of algorithm after result

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Algorithm Example

• Define the algorithm for mailing a letter, from
  obtaining the envelope to placing it in the
  mailbox

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Mailing a Letter

• Obtain Envelope
• If letter is too big, fold letter
• Place letter in envelope
• Address Envelope
• Seal envelope
• Obtain stamp
• Affix stamp
• Place in mailbox

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Flowcharts

• Flowcharts are graphical and verbal illustrations
  of algorithms
• Flowcharts are useful in describing any
  step-by-step procedure
• Flowcharts make it easier to create programming
  code

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Flowchart Elements
begin
start, end
Specific shapes have specific roles in a
flowchart ...
Do Assignment 5
read x
input
print y
output
Pre-defined process, usually complex
x y x
computation
if x gt 0
comparison or decision
F
T
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Flowcharts
Is letter bigger than envelope?
yes
obtain envelope
start
fold letter
no
insert into envelope
address envelope
obtain stamp
seal envelope
affix stamp
place in mailbox
end
raise flag
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Flowchart Checklist

• All major elements of the algorithm are
  indicated.
• The elements are clearly labeled.
• Sequence of elements is clear and there are no
  gaps or dead ends.
• Sequence of elements is logical from user's point
  of view.
• Flowchart symbols are used correctly.

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Decimal number to binary number
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Decimal number to binary number
Print The Remain to the left of previous remains
Divide the Number By 2
Start
Get a number
Is the quotient Equal to 1?
No
Print 1 To the left of Previous remains
Yes
End
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Pseudo code

• Flow chart in a text form.
• More like a computer program, but with human
  language.
• Can be easily translated into computer languages.

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Elements of pseudo code

• IF condition is true THEN
• Process step (1)
• ELSE
• Process step (2)
• GOTO
• Unconditional jump

If condition Is true
Process Step (1)
Process Step (2)
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Example Binary2Decimal

• Get a number
• IF the number is equal to 1 or 0
• Print the number END
• Divide the number by 2
• IF quotient is 1 THEN
• Print 1 to the left of the previous remains
• ELSE
• Print the remain to the left of previous
  remains. GOTO 3
• END

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Binary-ASCII conversion

• Each letter is represented by an 8-bit binary
  number, called ASCII (American Standard Code for
  Information Interchange. )
• Binary to Base Ten
• Base Ten to ASCII
• Details?

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Steps in Binary-ASCII

• Input number
• Break number up into eight bits
• Compute base two values for each bit
• Sum base two values to get base ten value
• Using base ten number, look in ASCII chart
• Output ASCII character
• Is there another number?
• Repeat procedure

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Pre-lab Assignment

• Using the steps of the Binary-ASCII conversion,
  create a flowchart, using the proper shapes,
  arrows, etc.
• In Fridays Lab we will use Powerpoint to create
  flow chart.