Provide CFG example

images/cfg.dot

@@ -0,0 +1,19 @@
+digraph "CFG" {
+    nodesep=0.6
+    node [shape=box, fontname="Roboto Mono", fontsize=11]
+
+    B1 [xlabel="B1", label="s = 0\li = 0\ln = 10\l"];
+    B2 [xlabel="B2", label="t1 = a - b\lifz t1 goto B4\l"];
+    B3 [xlabel="B3", label="t2 = i * 4\ls  = s + t2\l"];
+    B4 [xlabel="B4", label="s = s + i"];
+    B5 [xlabel="B5", label="i  = i + 1\lt3 = n - i\lifnz t3 goto B2\l"];
+    B6 [xlabel="B6", label="t4 = a - b"];
+
+    B1 -> B2;
+    B2 -> B3 [label="F"];
+    B2 -> B4 [label="T"];
+    B3 -> B5;
+    B4 -> B5;
+    B5 -> B6 [label="F"];
+    B5 -> B2 [label="T"];
+}

specification.md

@@ -370,6 +370,31 @@ This graph is commonly used by analyses for extracting structural information cr
 
 It is recommended to also provide a visitor mechanism for this graph.
 
+Like the AST, it can be visualised.
+The example below is taken from [Marc Moreno Maza](http://www.csd.uwo.ca/~moreno/CS447/Lectures/CodeOptimization.html/node6.html).
+
+Given this example IR:
+
+```
+    s = 0
+    i = 0
+    n = 10
+L1: t1 = a - b
+    ifz t1 goto L2
+    t2 = i * 4
+    s  = s + t2
+    goto L3
+L2: s = s + i
+L3: i  = i + 1
+    t3 = n - i
+    ifnz t3 goto L1
+    t4 = a - b
+```
+
+The visualisation of the corresponding CFG could look like this:
+
+![CFG Example](images/cfg.png)
+
 ### Assembly Code Generation
 
 The mC compiler targets x86 and uses GCC as back-end compiler.