Add Comment comparison and simple casting comparison

Nim-for-C-programmers.md

@@ -126,7 +126,49 @@ Note: Code examples are not exactly one-to-one, there may be subtle differences
     <th>C</th><th>Nim</th><th>Comment</th>
   </tr>
 
-
+  <tr>
+<td>
+<pre>
+/* This is a single-line comment */
+int x = 3;  // another single-line comment
+// So is this
+</pre>
+<pre>
+/*
+a multi-line comment
+*/
+//
+// or maybe this way?
+//
+#if 0
+    some code including comments to be ignored
+#endif
+</pre>
+</td>
+<td>
+<pre>
+# This is a single-line comment
+var x = 3   #  another comment
+</pre>
+<pre>
+discard """
+a multi-line comment
+"""
+#
+# or maybe this way?
+#
+when false:
+  a multi-line comment 
+  (but must be indented to be included)
+</pre>
+</td>
+<td>
+<b>Single line comments</b>. Use the hash char (#).
+<br>
+<br>
+<b>Multi-line comments</b>. Readability vs easy of use?
+</td>
+  </tr>
   <tr>
 <td>
 <pre>
@@ -304,5 +346,41 @@ proc foobar(a: ref TPerson) =
 <td><b>Dereference.</b> <i>In C, only the pointer to the strings in the struct is copied. In Nim, the string is also copied, but refs are not deep-copied.</i> </td>
   </tr>
 
+  <tr>
+<td>
+<pre>
+double d = 3.1415926;
+int i = (int) d;
+d = (double) i;
+printf(%d, %g\n", i, d);
+</pre>
+<pre>
+int x = 42;
+void *p = &x;
+int y = (int) *p;
+printf("%d, %d, %p\n", x, y, p);
+</pre>
+</td>
+<td>
+<pre>
+var d: float = 3.1415926
+var i = d.int
+d = i.float
+echo i, " ",d
+</pre>
+<pre>
+var 
+  x = 42
+  p: pointer = x.addr
+  y = cast[ptr int](p)[]
+echo x, " ", y, " ", repr(p)
+</pre>
+</td>
+<td>
+<b>Simple casting</b> Considered unsafe in Nim (and that you know what you are doing).
+<br>
+cast is NOT for numeric type conversion.
+</td>
+  </tr>
 
 </table>