add listing tags

Author: habibasorour

source/ch5_loopsanditeration.ptx

@@ -176,19 +176,22 @@ public class StringIterationExample {
             Both Python and Java support the <c>while</c> loop, which continues to execute as long as a condition is true.
             Here is a simple example in Python that counts down from 5:
         </p>
-        <program xml:id="python-countdown" interactive="activecode" language="python">
+        <listing xml:id="python-countdown">
+        <program interactive="activecode" language="python">
             <code>
 i = 5
 while i &gt; 0:
     print(i)
     i = i - 1
             </code>
         </program>
+        </listing>
 
         <p>
             In Java, we add parentheses and curly braces. Here is the same countdown loop in Java:
         </p>
-        <program xml:id="java-countdown" interactive="activecode" language="java">
+        <listing xml:id="java-countdown">
+        <program interactive="activecode" language="java">
             <code>
 public class WhileLoopExample {
     public static void main(String[] args) {
@@ -201,6 +204,7 @@ public class WhileLoopExample {
 }
             </code>
         </program>
+        </listing>
 
         <p><idx><c>do-while</c> loop</idx>
             Java adds an additional, if seldom used variation of the <c>while</c> loop called the <c>do-while</c> loop.
@@ -209,8 +213,8 @@ public class WhileLoopExample {
             Some programmers prefer this loop in some situations because it avoids an additional assignment prior to the loop.
             For example, the following loop will execute once even though the condition is initially false.
         </p>
-
-        <program xml:id="java-do-while" interactive="activecode" language="java">
+        <listing xml:id="java-do-while">
+        <program interactive="activecode" language="java">
             <code>
 public class DoWhileExample {
     public static void main(String[] args) {
@@ -222,6 +226,8 @@ public class DoWhileExample {
 }
             </code>
         </program>
+        </listing>
+        
     </section>
     <section xml:id="chapter5_summary">
         <title>Summary &amp; Reading Questions</title>