Pigeon Hole Device

1
Pigeon Hole Device

• What does it resemble?
• What can it do?
• How could it be improved?
• Will it ever look familiar?
• How much memory does it have?
• What kind of problems does it have?

2
Nine empty boxes numbered from 1 to 9.
1
3
Lets put something in the boxes and see what
happens.
1
4
After execution of first command in box 1.
2
5
After execution of command in box 2.
3
6
After execution of command in box 3.
4
7
After execution of command in box 4.
2
8
After execution of command in box 2.
3
9
After execution of command in box 3.
4
10
After execution of command in box 4.
2
11
After execution of command in box 2.
3
12
After execution of command in box 3.
4
13
After execution of command in box 4.
5
14
After execution of command in box 5. Stopped!
0
15
Ring any bells?

• What does it look like?
• Initialize, Loop, Terminate (Which box)
• Variables, Constants, Values?
• How could we improve the model

16
Improvements?

• Labels, Identifiers, Names for stuff
• Memory contents? Fixed / Variable
• Registers?
• Indirect addressing? (Box 1)
• Move (Box7) to Box 3
• Outside I/O (Files, etc?)
• I/O Commands (Read and Write?)