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Sample programs to predict output. Try these. See if you can predict the output. Change them and try again. Email others with your example code.
<?xml version = "1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!-- Fig. 8.7: average.html -->
<!-- Class Average Program -->
<html xmlns = "http://www.w3.org/1999/xhtml">
<head>
<title>Class Average Program</title>
<script type = "text/javascript">
<!--
var a=1, b=7, c=9;
while ( a < c )
{
document.writeln("Junk" + a + "<br>");
a= a + 2;
}
// -->
</script>
</head>
<body>
<p>Click Refresh (or Reload) to run the script again</p>
</body>
</html>
Example 2
<?xml version = "1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!-- Fig. 8.7: average.html -->
<!-- Class Average Program -->
<html xmlns = "http://www.w3.org/1999/xhtml">
<head>
<title>Class Average Program</title>
<script type = "text/javascript">
<!--
var a=1, b=7, c=9;
while ( a < c )
{
document.writeln("Junk" + a + "<br>");
if (a ==3)
{
a++;
document.writeln("Stuff" + a + "<br>");
}
if (a == 5)
document.writeln("Skip" + a + "<br>");
if (a < 8)
{
b = b - 1;
if ( a < 5)
document.writeln("Small" + b + "<br>");
}
document.writeln("Again" + a + "<br>");
a = a + 2
}
// -->
</script>
</head>
<body>
<p>Click Refresh (or Reload) to run the script again</p>
</body>
</html>
Example 3.
<?xml version = "1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<!-- Fig. 8.7: average.html -->
<!-- Class Average Program -->
<html xmlns = "http://www.w3.org/1999/xhtml">
<head>
<title>Class Average Program</title>
<script type = "text/javascript">
<!--
var a=1, b=7, c=9;
while ( a < c )
{
document.writeln("Junk" + a + "<br>");
if (a ==3)
{
while ( b > 2)
{
document.writeln("Loop" + b + "<br>");
if ( b == 3)
{
document.writeln("go" + b + "<br>");
b=b-2;
}
b--;
}
}
if (a == 5)
document.writeln("Skip" + a + "<br>");
if (a > 7)
{
b = b - 1;
if ( a < 5)
document.writeln("Small" + b + "<br>");
}
document.writeln("Again" + a + "<br>");
a = a + 2
}
// -->
</script>
</head>
<body>
<p>Click Refresh (or Reload) to run the script again</p>
</body>
</html>
Challenge
There is a WebX discussion group called Output Challenge. Your task is to write a program that is hard to trace and post it to the website. Make sure it works first. Here are the rules:
1. Use 3 integer variables. No fractions
2. Keep the numbers generated less than 20.
3. Use only +, -, *, /, and % operators
4. The code should be less than 20 lines long
5. Use only ==, >, or < in your if and while
6. Use only if and while, along with assignment statements
7. Have at most 2 while statements
8. Keep the output to 20 lines or less
See how hard you can make the flow of control. We will have a vote on the best program online.
More Examples:
<?xml version = "1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" >
<!-- Fig. 8.7: average.html -->
<!-- Class Average Program -->
<html xmlns = "http://www.w3.org/1999/xhtml">
<head>
<title>Class Average Program</title>
<script type = "text/javascript">
<!--
var a=1, b=8, c=9;
if ( a < c )
{
document.writeln("No" + a + "<br>");
while (a < b)
{
document.writeln("Junk" + a + "<br>");
if (a < 3)
{
a = a + 2;
document.writeln("Stuff" + a + "<br>");
}
if (a == 5)
{
document.writeln("Skip" + a + "<br>");
if (a < 8)
{
b = b - 1;
if ( a < 5)
document.writeln("Small" + b + "<br>");
}
}
document.writeln("Again" + a + "<br>");
a = a + 2
}
}
// -->
</script>
</head>
<body>
<p>Click Refresh (or Reload) to run the script again</p>
</body>
</html>
Another Example
<?xml version = "1.0"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd" >
<!-- Fig. 8.7: average.html -->
<!-- Class Average Program -->
<html xmlns = "http://www.w3.org/1999/xhtml">
<head>
<title>Class Average Program</title>
<script type = "text/javascript">
<!--
{
var a,b,c;
a=0; b=5; c=9;
while ( a < c )
{
document.writeln("Junk" + a+ "<br>");
a= a + 2;
if ( a > 4)
{
document.writeln("loop"+ "<br>");
a++;
}
if ( a<4 )
{
document.writeln("little" + a+ "<br>");
c--;
}
}
if ( b == 7 )
document.writeln("do again"+ "<br>");
while ( b < 10 )
{
b++;
if (b == 9)
document.writeln("NOPE"+ "<br>");
document.writeln("skip"+ "<br>");
}
document.writeln(b+ "<br>");
if ( b > 10 )
document.writeln("done"+ "<br>");
document.writeln("again" + b+ "<br>");
}
// -->
</script>
</head>
<body>
<p>Click Refresh (or Reload) to run the script again</p>
</body>
</html>
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