Archive:Debugging challenges

These debugging challenges are written in JavaScript, and designed to complement the units: ICAB4225A Automate processes and ICAT4221A Locate equipment, system and software faults

Challenge Set 1 - Lexical Errors

Lexical errors are introduced when the programmer enters symbols that are not part of the programming language. Unlike when you misspell a word in English, this inevitably leads to a breakdown in programming communications. See if you can see (or find) the lexical errors in the following code snippets...

<script type="text/javascript">
   var num1 = 2;
   var num2 = 3;
   var product = num1 x num2;
   alert("the product of " + num1 + " and " + num2 + " is " + product);
</script>

<script type="text/javascript"> /* This script and many more are available free online at The JavaScript Source!! http://javascript.internet.com Created by: Patrick Fitzgerald | http://www.barelyfitz.com/ */ function truncate() { var len = 100; var p = document.getElementByID('truncateMe'); if (p) { var trunc = p.innerHTML; if (trunc.length > len) {

/* Truncate the content of the P, then go back to the end of the previous word to ensure that we don't truncate in the middle of a word */ trunc = trunc.substring(0, len); trunc = trunc.replace(/\w+$/, );

/* Add an ellipses to the end and make it a link that expands the paragraph back to its original size */ trunc += '<a href="#" ' + 'onclick="this.parentNode.innerHTML=' + 'unescape(\+escape(p.innerHTML)+'\');return false;">' + '[ more ... ]<\/a>'; p.innerHTML = trunc; } } }

// Multiple onload function created by: Simon Willison // http://simon.incutio.com/archive/2004/05/26/addLoadEvent function addLoadEvent(func) { var oldonload = window.onload; if (typeof window.onload != 'function') { window.onload = func; } else { window.onload = function() { if (oldonload) { oldonload(); } func(); } } }

addLoadEvent(function() { truncate(); }); </script>

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Challenge 2 - Syntactic Errors

A syntax error occurs when you use the right symbols, but in a way that doesn't make sense to the compiler or interpreter. Something like the English sentence: "You don't program good"

 <script type="text/javascript">
   var x;
   x=prompt("What is 5 x 5?");
   while (x != 25) do
   {
     alert("Wrong answer");
     x=prompt("What is 5 x 5?",0);
   }
   document.write("Right, the answer is " + x)
 </script>

Challenge 3 - Execution Errors

Execution errors are impossible requests made in perfectly correct programming terms.

 <script type="text/javascript">
   var weekdays=new Array("Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday")
   for (i=1; i<8; ++i)
   {
     document.write(weekdays[i] + "
");
   }    
 </script> 

Challenge 4 - Logic Errors

These are errors introduced Through faulty design. Once again, the syntax is correct, but the results are unexpected

TODO - add more examples of each