Simple Stack Machine

                              +----------------------------------------------------------------+
                              |                                                                |
                              |    ---------------                                             |
+-------------+               |    |             |              registers  +-------------+     |
|             |               |    |             |                         |     sp      |     |
|    data     | <-----------> |    |             |                         |-------------|     |
|    memory   |               |    |             v                         |     fp      |     |
|             |               |    |      +-------------+                  ---------------     |
+-------------+               |    |      |    fetch    |                  |     ip      |     |
                              |    |      +-------------+                  +-------------+     |
                              |    |      +-------------+                                      |
                              |    |      |    decode   |                  +-------------+     |
                              |    |      +-------------+                  |             |     |
                              |    |      +-------------+                  |             |     |
+-------------+               |    |      |   execute   |                  |             |     |
|             |               |    |      +-------------+                  ---------------     |
|    code     | <-----------> |    |                                       |             |     |
|    memory   |               |    |             |                         ---------------     |
|             |               |    |             |                         |             |     |
+-------------+               |    |             |                 stack   +-------------+     |
                              |    |-------------+                                             |
                              |                                                                |
                              +----------------------------------------------------------------+