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Algorithms

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Algorithms Powered By Docstoc
					    ISP 121
     Algorithms
        and
Computer Programming
 Why Know Simple Programming?
 You  can create powerful macros in Access
  / Excel / Word / ??? to manipulate data
 You can create interactive web pages,
  such as the DePaul QRC mapping tool
 You can write simple programs to analyze
  data and write the next article exposing
  cheaters in your school district
       What is an Algorithm?
 Computers   require precise instructions to
  perform an operation
 The instructions cannot be ambiguous
 An algorithm is an ordered sequence of
  instructions that is guaranteed to solve a
  specific problem
         What is an Algorithm?
 Algorithmsconsist of three basic types of
 operations or instructions:
     Sequential operations, e.g. Add 1 cup of
      butter; Subtract the amount of the check from
      the current account balance; Set the value of
      x to 1
     Conditional operations, e.g. If the mixture is
      too dry, then add ½ cup water; If the current
      account balance < 0, then account overdrawn
         What is an Algorithm?
 Algorithmsconsist of three basic types of
 operations or instructions:
     Iterative operations, e.g. Repeat the previous
      two steps until the mixture has thickened;
      Repeat the following five steps until there are
      no more checks to be processed; Repeat
      steps 1,2 and 3 until the value of y is equal to
      +1
                        Example
 Add   two values:
                     32542
                   + 42892



 How would you describe this operation to someone who has never seen
 carry arithmetic?
  Average Miles Per Gallon (1)
 Step  1: Get values for gallons used,
  starting mileage, ending mileage
 Step 2: Set the value of distance driven to
  (ending mileage – starting mileage)
 Step 3: Set the value of average miles per
  gallon to (distanced driven / gallons used)
 Step 4: Print the value of average miles
  per gallon
 Step 5: Stop
Average Miles Per Gallon(2)
  Step  1: Get values for gallons used,
   starting mileage, ending mileage
  Step 2: Set the value of distance
   driven to (ending mileage – starting
   mileage)
  Step 3: Set the value of average
   miles per gallon to (distanced driven /
   gallons used)
  Step 4: Print the value of average
   miles per gallon (more on next slide)
  Average Miles Per Gallon(2)
 Step5: If average miles per gallon is
 greater than 25.0 then
   Print the message “You are getting good gas
    mileage.”
  Else
   Print the message “You are NOT getting good

    gas mileage.”
 Step   6: Stop
  Average Miles Per Gallon (3)
     1: Repeat step 2 to step 8 until
 Step
 Response is No
     Step 2: Get values for gallons used, starting
      mileage, ending mileage
     Step 3: Set the value of distance driven to
      (ending mileage – starting mileage)
     Step 4: Set the value of average miles per
      gallon to (distanced driven / gallons used)
     Step 5: Print the value of average miles per
      gallon
 Average Miles Per Gallon (3)
     Step 6: If average miles per gallon is greater
      than 25.0 then
       • Print the message “You are getting good gas
         mileage.”
      Else
       • Print the message “You are NOT getting good gas
         mileage.”
     Step 7: Print the message “Do you want to do
      this again, Yes or No?”
     Step 8: Get a value for Response from the
      user
 Step   9: Stop
                 HTML
 Hyper-Text  Markup Language
 All web pages are made (to varying
  degrees) from HTML
 Each HTML command tells the web
  browser what to do next, such as start a
  new paragraph, display an image, or insert
  a link
<HTML>                               Begins every HTML document
<HEAD>                               Begins the head section
<TITLE>DePaul University
</TITLE>                             Title that appears on browser title bar
</HEAD>                              Ends the head section

<BODY>                               Begins the body section
This is the first line.<BR>          Text followed by line Break
<P>Start a new paragraph.</P>        Begins a new paragraph
<H1>First Heading</H1>               Level 1 heading (biggest)
<H2>A second level heading</H2>      Level 2 heading (little smaller)

<HR>                                 Inserts a horizontal rule (straight line)
<B>This line is bold.</B><BR>        Bold text
<I>This line is italicized</I><BR>   Italicized text
<IMG SRC=“\images\banner.gif”>       Insert an image here

<A HREF=“http://www.cs.depaul.edu”>
  DePaul CS Page</A>             Link to another web page

</BODY>                              Close the body section
</HTML>                              Ends every HTML document
               JavaScript
 JavaScript can be added to an HTML
  document to provide dynamic features
 JavaScript can be added to the head or
  body of HTML code (but we will
  concentrate on examples in body), can
  assign values to variables, can perform
  decision statements, and can perform loop
  statements
Example - JavaScript in Body
 <html>
 <head>
 </head>

 <body>

 <script type="text/javascript">
 document.write("This message is written when the page loads")
 </script>

 </body>
 </html>
Example - JavaScript in Body
 <html>
 <head>
 </head>

 <body>

 <script type="text/javascript">
 alert("This message is written inside an Alert box")
 </script>

 </body>
 </html>
Example - Using a Variable
<html>
<body>

<script type="text/javascript">
var name

name = prompt(“Please enter a name”)
document.write(name)

</script>
</body>
</html>
  Example - Using an If
<html>
<body>

<script type="text/javascript">
var d = new Date()
var time = d.getHours()

if (time < 12)
{
     document.write("<b>Good morning</b>")
}
</script>

<p>This example demonstrates the If statement.</p>

<p>If the time on your browser is less than 12,
you will get a "Good morning" greeting.</p>
</body>
</html>
Example - Using an If…Else
  <html>
  <body>
  <script type="text/javascript">
  var d = new Date()
  var time = d.getHours()
  if (time < 12)
  {
       document.write("<b>Good morning</b>")
  }
  else
  {
       document.write("<b>Good afternoon</b>")
  }
  </script>
  <p>This example demonstrates the If...Else statement.</p>
  <p>If the time on your browser is less than 12,
  you will get a "Good morning" greeting.
  Otherwise you will get a "Good day" greeting.</p>
  </body>
  </html>
        Logical Operators
 Youcan use the following logical
 operators in IF and WHILE statements
  ==
  !=
  >
  >=
  <
  <=
 Example - Using a While to Count
<html>
<body>
<script type="text/javascript">
var i = 0
while (i <= 5)
{
   document.write("The number is " + i)
   document.write("<br>")
   i++
}
</script>
<p>Explanation:</p>
<p><b>i</b> equal to 0.</p>
<p>While <b>i</b> is less than , or equal to, 5, the loop will continue to run.</p>
<p><b>i</b> will increase by 1 each time the loop runs.</p>

</body>
</html>
Example - Using a While to Prompt
<html>
<body>
<script type="text/javascript">
var answer
answer = prompt(“Do you understand quantum physics?”)
while (answer == “no”)
{
document.write(“It is actually based on quantum things.")
answer = prompt(“Now do you understand quantum physics?”)
}
document.write(“Congrats!”)
</script>

</body>
</html>

				
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