example: $fib$ -- a function can call itself: our rules still work!

file fib.m
+----------------------------------+
| function x = fib(n)              |
|     if n < 2			   |
| 	  x = n;		   |
|     else			   |
| 	  x = fib(n-1) + fib(n-2); |
|     end                          |
+----------------------------------+

run $fib(3)$ inside command window; this time, we omit the BIG
enclosing scope:

+---------+
|command  |
|+----+   |
|| [] |   |
|+----+   |
+---------+

+----------------+				>fib(3)
|command  fib_3  |				     |
|+----+   +----+ |				     |
|| [] |   | [] | |				     |
|+----+   +----+ |				     |
+----------------+				     |
						     |
+---------------------+				     |
|command  fib_3       |				     |
|+----+   +---------+ |				     |
|| [] |   |   +---+ | |				     |
|+----+   | n | 3 | | |				     |
|         |   +---+ | |				     |
|         +---------+ |				     |
+---------------------+				     |
                                                     |
+------------------------------+		     |  >fib(2)
|command  fib_3       fib_3_2  |                     |	     |
|+----+   +---------+ +----+   |		     |	     |
|| [] |   |   +---+ | | [] |   |		     |	     |
|+----+   | n | 3 | | +----+   |		     |	     |
|         |   +---+ |          |		     |	     |
|         +---------+          |		     |	     |
+------------------------------+		     |	     |
						     |	     |
+---------------------------------+		     |	     |
|command  fib_3       fib_3_2     |		     |	     |
|+----+   +---------+ +---------+ |		     |	     |
|| [] |   |   +---+ | |   +---+ | |		     |	     |
|+----+   | n | 3 | | | n | 2 | | |		     |	     |
|         |   +---+ | |   +---+ | |		     |	     |
|         +---------+ +---------+ |		     |	     |
+---------------------------------+		     |	     |
						     |	     |
+--------------------------------------------+	     |       |  >fib(1)
|command  fib_3       fib_3_2     fib_3_2_1  |	     |	     |	     |
|+----+   +---------+ +---------+ +----+     |	     |	     |	     |
|| [] |   |   +---+ | |   +---+ | | [] |     |	     |	     |	     |
|+----+   | n | 3 | | | n | 2 | | +----+     |	     |	     |	     |
|         |   +---+ | |   +---+ |            |	     |	     |	     |
|         +---------+ +---------+            |	     |	     |	     |
+--------------------------------------------+	     |	     |	     |

						     |	     |	     |
+---------------------------------------------+	     |	     |	     |
|command  fib_3       fib_3_2     fib_3_2_1   |	     |	     |	     |
|+----+   +---------+ +---------+ +---------+ |	     |	     |	     |
|| [] |   |   +---+ | |   +---+ | |   +---+ | |	     |	     |	     |
|+----+   | n | 3 | | | n | 2 | | | n | 1 | | |	     |	     |	     |
|         |   +---+ | |   +---+ | |   +---+ | |	     |	     |	     |
|         +---------+ +---------+ +---------+ |	     |	     |	     |
+---------------------------------------------+	     |	     |	     |
						     |	     |	     |
+---------------------------------------------+	     |	     |	     |
|command  fib_3       fib_3_2     fib_3_2_1   |	     |	     |	     |
|+----+   +---------+ +---------+ +---------+ |	     |	     |	     |
|| [] |   |   +---+ | |   +---+ | |   +---+ | |	     |	     |	     |
|+----+   | n | 3 | | | n | 2 | | | n | 1 | | |	     |	     |	     |
|         |   +---+ | |   +---+ | |   +---+ | |	     |	     |	     |
|         +---------+ +---------+ |   +---+ | |	     |	     |	     |
|                                 | x | 1 | | |	     |	     |	     |
|                                 |   +---+ | |	     |	     |	     |
|                                 +---------+ |	     |	     |	     |
+---------------------------------------------+	     |	     |	     |
						     |	     |	     |
+---------------------------------+		     |       |  <fib(1)
|command  fib_3       fib_3_2     |		     |	     |
|+----+   +---------+ +---------+ |		     |	     |
|| [] |   |   +---+ | |   +---+ | |		     |	     |
|+----+   | n | 3 | | | n | 2 | | |		     |	     |
|         |   +---+ | |   +---+ | |		     |	     |
|         +---------+ +---------+ |		     |	     |
+---------------------------------+		     |	     |
						     |	     |
+--------------------------------------------+	     |       |  >fib(0)
|command  fib_3       fib_3_2     fib_3_2_0  |	     |	     |	     |
|+----+   +---------+ +---------+ +----+     |	     |	     |	     |
|| [] |   |   +---+ | |   +---+ | | [] |     |	     |	     |	     |
|+----+   | n | 3 | | | n | 2 | | +----+     |	     |	     |	     |
|         |   +---+ | |   +---+ |            |	     |	     |	     |
|         +---------+ +---------+            |	     |	     |	     |
+--------------------------------------------+	     |	     |	     |
						     |	     |	     |
+---------------------------------------------+	     |	     |	     |
|command  fib_3       fib_3_2     fib_3_2_0   |	     |	     |	     |
|+----+   +---------+ +---------+ +---------+ |	     |	     |	     |
|| [] |   |   +---+ | |   +---+ | |   +---+ | |	     |	     |	     |
|+----+   | n | 3 | | | n | 2 | | | n | 0 | | |	     |	     |	     |
|         |   +---+ | |   +---+ | |   +---+ | |	     |	     |	     |
|         +---------+ +---------+ +---------+ |	     |	     |	     |
+---------------------------------------------+	     |	     |	     |
						     |	     |	     |
+---------------------------------------------+	     |	     |	     |
|command  fib_3       fib_3_2     fib_3_2_0   |	     |	     |	     |
|+----+   +---------+ +---------+ +---------+ |	     |	     |	     |
|| [] |   |   +---+ | |   +---+ | |   +---+ | |	     |	     |	     |
|+----+   | n | 3 | | | n | 2 | | | n | 0 | | |	     |	     |	     |
|         |   +---+ | |   +---+ | |   +---+ | |	     |	     |	     |
|         +---------+ +---------+ |   +---+ | |	     |	     |	     |
|                                 | x | 0 | | |	     |	     |	     |
|                                 |   +---+ | |	     |	     |	     |
|                                 +---------+ |	     |	     |	     |
+---------------------------------------------+	     |	     |	     |

						     |	     |	     |
+---------------------------------+		     |       |  <fib(0)
|command  fib_3       fib_3_2     |		     |	     |
|+----+   +---------+ +---------+ |		     |	     |
|| [] |   |   +---+ | |   +---+ | |		     |	     |
|+----+   | n | 3 | | | n | 2 | | |		     |	     |
|         |   +---+ | |   +---+ | |		     |	     |
|         +---------+ +---------+ |		     |	     |
+---------------------------------+		     |	     |
						     |	     |
+---------------------------------+		     |	     |
|command  fib_3       fib_3_2     |		     |	     |
|+----+   +---------+ +---------+ |		     |	     |
|| [] |   |   +---+ | |   +---+ | |		     |	     |
|+----+   | n | 3 | | | n | 2 | | |		     |	     |
|         |   +---+ | |   +---+ | |		     |	     |
|         +---------+ |   +---+ | |		     |	     |
|                     | x | 1 | | |		     |	     |
|                     |   +---+ | |		     |	     |
|                     +---------+ |		     |	     |
+---------------------------------+		     |	     |
						     |	     |
+---------------------+				     |  <fib(2)
|command  fib_3       |				     |
|+----+   +---------+ |				     |
|| [] |   |   +---+ | |				     |
|+----+   | n | 3 | | |				     |
|         |   +---+ | |				     |
|         +---------+ |				     |
+---------------------+				     |
						     |
+------------------------------+		     |  >fib(1)
|command  fib_3       fib_3_1  |		     |	     |
|+----+   +---------+ +----+   |		     |	     |
|| [] |   |   +---+ | | [] |   |		     |	     |
|+----+   | n | 3 | | +----+   |		     |	     |
|         |   +---+ |          |		     |	     |
|         +---------+          |		     |	     |
+------------------------------+		     |	     |
						     |	     |
+---------------------------------+		     |	     |
|command  fib_3       fib_3_1     |		     |	     |
|+----+   +---------+ +---------+ |		     |	     |
|| [] |   |   +---+ | |   +---+ | |		     |	     |
|+----+   | n | 3 | | | n | 1 | | |		     |	     |
|         |   +---+ | |   +---+ | |		     |	     |
|         +---------+ +---------+ |		     |	     |
+---------------------------------+		     |	     |
						     |	     |
+---------------------------------+		     |	     |
|command  fib_3       fib_3_1     |		     |	     |
|+----+   +---------+ +---------+ |		     |	     |
|| [] |   |   +---+ | |   +---+ | |		     |	     |
|+----+   | n | 3 | | | n | 1 | | |		     |	     |
|         |   +---+ | |   +---+ | |		     |	     |
|         +---------+ |   +---+ | |		     |	     |
|                     | x | 1 | | |		     |	     |
|                     |   +---+ | |		     |	     |
|                     +---------+ |		     |	     |
+---------------------------------+		     |	     |

						     |	     |
+---------------------+				     |  <fib(1)
|command  fib_3       |				     |
|+----+   +---------+ |				     |
|| [] |   |   +---+ | |				     |
|+----+   | n | 3 | | |				     |
|         |   +---+ | |				     |
|         +---------+ |				     |
+---------------------+				     |
						     |
+---------------------+				     |
|command  fib_3       |				     |
|+----+   +---------+ |				     |
|| [] |   |   +---+ | |				     |
|+----+   | n | 3 | | |				     |
|         |   +---+ | |				     |
|         |   +---+ | |				     |
|         | x | 2 | | |				     |
|         |   +---+ | |				     |
|         +---------+ |				     |
+---------------------+				     |
						     |
+---------+					<fib(3)
|command  |
|+----+   |
|| [] |   |
|+----+   |
+---------+

+--------------+
|command       |
|+-----------+ |
||     +---+ | |
|| ans | 2 | | |
||     +---+ | |
|+-----------+ |
+--------------+
_______________________________________________________________________________

note: 
+ you can download $strhcat.m$ (used by $boxscope$) and $boxscope.m$
  to help you draw your own box scope diagram pictures
  + (note: don't try to read the code -- it's complicated!)
+ pictures above were (edited from) the output of the code below

clc; clear
diary on
big.command = [];		disp(boxscope(big,1))
big.fib_3 = [];			disp('>fib(3)'); disp(boxscope(big,1))
big.fib_3.n = 3;		disp(boxscope(big,1))
big.fib_3_2 = [];		disp('>fib(3) >fib(2)'); disp(boxscope(big,1))
big.fib_3_2.n = 2;		disp(boxscope(big,1))
big.fib_3_2_1 = [];		disp('>fib(3) >fib(2) >fib(1)'); disp(boxscope(big,1))
big.fib_3_2_1.n = 1;		disp(boxscope(big,1))
big.fib_3_2_1.x = 1;		disp(boxscope(big,1))
big=rmfield(big,'fib_3_2_1');	disp('>fib(3) >fib(2) <fib(1)'); disp(boxscope(big,1))
big.fib_3_2_0 = [];		disp('>fib(3) >fib(2) >fib(0)'); disp(boxscope(big,1))
big.fib_3_2_0.n = 0;		disp(boxscope(big,1))
big.fib_3_2_0.x = 0;		disp(boxscope(big,1))
big=rmfield(big,'fib_3_2_0');	disp('>fib(3) >fib(2) <fib(0)'); disp(boxscope(big,1))
big.fib_3_2.x = 1;		disp(boxscope(big,1))
big=rmfield(big,'fib_3_2');	disp('>fib(3) <fib(2)'); disp(boxscope(big,1))
big.fib_3_1 = [];		disp('>fib(3) >fib(1)'); disp(boxscope(big,1))
big.fib_3_1.n = 1;		disp(boxscope(big,1))
big.fib_3_1.x = 1;		disp(boxscope(big,1))
big=rmfield(big,'fib_3_1');	disp('>fib(3) <fib(1)'); disp(boxscope(big,1))
big.fib_3.x = 2;		disp(boxscope(big,1))
big=rmfield(big,'fib_3');	disp('<fib(3)'); disp(boxscope(big,1))
big.command.ans = 2;		disp(boxscope(big,1))
diary off
_______________________________________________________________________________

[3/02] 

+ re-download $strhcat.m$ (used by $boxscope$) and $boxscope.m$
  and download and run $boxfib.m$ to see an animated trace!