1. Data structures

2. D1 Data structures
The features, applications and implications of data types used in computer systems:
stack
queue
array
list.
The use and application of data types in computer software.
The use and implications of data types in computer hardware.

3. Representation of Data as Bit Patterns – Data Structures – Linked-list
A linked list is usually represented by the following diagram
End
Start
Free Space
Free
End
Data
Address of next node
Node

4. Representation of Data as Bit Patterns – Data Structures – Linked - list
The Free Space is the available memory that the linked-list can grow into
Data can be added and removed from any point
A node contains two pieces of information
Left the data
Right the address of the next node

5. Representation of Data as Bit Patterns – Data Structures – Linked - list
Adding and deleting from a linked-list involves changing the pointers to either incorporate a new node (adding) or redirecting to miss out an existing node (deleting)
The new node will be added from the free space
The deleted node will be added to the free space
There are 3 possible positions that a node can be added or deleted
Start of the list
End of the list
‘Middle’ of the list

6. Representation of Data as Bit Patterns – Data Structures – Linked - list
If the start of the list is be changed the initial start value needs to be altered to point to the new node
If the end of the list is to be changed the new last node needs to be altered so it represents the end of the list
Middle nodes have no particular problems

7. Representation of Data as Bit Patterns – Data Structures – Linked – list
Given the following linked-list 1 B 2 F 3 M 4
End

8. Representation of Data as Bit Patterns – Data Structures – Linked – list
The data “K” is to be added to the list 1 B 2 F 3 M 4
End

9. Representation of Data as Bit Patterns – Data Structures – Linked – list
“K” is then added to the free space 1 B 2 F 3 M 4
End
Free 5 K 6 7
End

10. Representation of Data as Bit Patterns – Data Structures – Linked – list
The appropriate pointers need moving 1 B 2 F 3 M 4
End
Free 5 K 6 7
End

11. Representation of Data as Bit Patterns – Data Structures – Linked – list
Joining the previous node to “K” 1 B 2 F 5 M 4
End
Free 5 K 6 7
End

12. Representation of Data as Bit Patterns – Data Structures – Linked – list
Linking “K” to the next node 1 B 2 F 5 M 4
End
Free 5 K 3 7
End

13. Representation of Data as Bit Patterns – Data Structures – Linked – list
Recovering the free space 1 B 2 F 3 M 4
End
Free 6 K 3 7
End

14. Representation of Data as Bit Patterns – Data Structures – Linked – list
The ‘new’ linked-list 1 B 2 F 5 M 4
End
Free 6 K 3 7
End

15. Representation of Data as Bit Patterns – Data Structures – Linked – list
Given the following linked-list 1 B 2 F 3 M 4
End

16. Representation of Data as Bit Patterns – Data Structures – Linked – list
“F” is to be deleted from the list 1 B 2 F 3 M 4
End

17. Representation of Data as Bit Patterns – Data Structures – Linked – list
“F” should be added to the free-space 1 B 2 F 3 M 4
End
Free 5 6 7
End

18. Representation of Data as Bit Patterns – Data Structures – Linked – list
“Redirecting the pointers 1 B 2 F 3 M 4
End
Free 5 6 7
End

19. Representation of Data as Bit Patterns – Data Structures – Linked – list
Redirecting around “F” 1 B 3 F 3 M 4
End
Free 5 6 7
End

20. Representation of Data as Bit Patterns – Data Structures – Linked – list
Adding “F” to the free-space 1 B 3 F 3 M 4
End
Free 2 6 7
End

21. Representation of Data as Bit Patterns – Data Structures – Linked – list
Adding “F” to the free-space 1 B 3 F 5 M 4
End
Free 2 6 7
End

22. Representation of Data as Bit Patterns – Data Structures – Linked – list
The ‘new’ linked list 1 B 3 F 5 M 4
End
Free 2 6 7
End

23. Representation of Data as Bit Patterns – Data Structures – Linked - list
Uses for a linked-list are any situation that would require data to be inserted and deleted at any point – hence retaining the original order of the list

24. Stack A Stack is a Last In, First Out (LIFO) data structure (or FILO)
Items can be added ‘PUSHED’ onto the stack. Items can be removed ‘POPPED’ from the stack
It is a dynamic structure as the size of the stack grows depending on how many items are on it. It is controlled by ONE pointer

25. Stacks [6] [5] [4] [3] [2] [1] Katie Millie Joe
Items can be pushed (add),
Its can be popped (remove)
Can only be added to the top of the Stack
maxStackSize = 6
top =3

26. Stacks

27. Push/Pop Pseudocode
Procedure Push If Top = MaxStackSize Then Write ‘Stack is full’ Else Add 1 to Top Stack[Top] := NewItem EndIf EndProc
Procedure Pop
If Top = 0
Then Write ‘Stack is empty’
Else
PoppedItem := Stack[Top]
Subtract 1 from Top
EndIf
EndProc

28. Uses of Stacks
To store return addresses, parameters, and register contents when subroutines are called
When sub routine is called, the return address is pushed onto the stack, until the sub has finished execution where it is then popped off.
Undo and Redo functions
Reverse Polish Notation

29. Queues

30. Queues
A Queue is a First In, First Out (FIFO) data structure (or LILO)
Data joins the queue at the rear. Data leaves the queue from the front
It is a dynamic data structure. It is controlled by TWO pointers
No data is added to a full queue. No data can be removed from an empty queue

31. Queue Declarations Frontpointer position of the first item
Rearpointer position of the last item
Max the maximum number allowed
Numberinqueue number currently in the queue

32. Queues Fred Jack Matt Ben Front Rear queueSize=4
Add a new item (to the rear)
Remove an item (from the front)

33. Uses of Queue Holding jobs waiting to be processed
Spooling output to a disk prior to printing
Both having the idea of dealing with tasks in the ‘first come, first served’ manner. It is the ‘fair’ approach.

34. STACKS AND QUEUES- RESEARCH
EXPLAIN WHAT A STACK IS
EXPLAIN WHAT A QUEUE IS
COMPUTER APPLICATIONS STACKS COULD BE USED FOR
COMPUTER APPLICATIONS QUEUES COULD BE USED FOR
LABELED DIAGRAM OF STACK
LABELED DIAGRAM OF QUEUE