1. Data and information These are philosophical categories These are philosophical categories We are not able to give exact definition We are not able to give exact definition In everyday life we use these concept as synonyms In everyday life we use these concept as synonyms We only have ideas about these words We only have ideas about these words 1

2. Definitions of Information Information is …. Information is …. “….. data processed for a purpose” R. Curtis “….. data processed for a purpose” R. Curtis “….. knowledge derived from data”. “….. knowledge derived from data”. “….. data placed within a context” D. Kroenke “….. data placed within a context” D. Kroenke “….. the amount of uncertainty that is reduced when a message is received” “….. the amount of uncertainty that is reduced when a message is received” Shannon and Weaver “….. a difference that makes a difference” “….. a difference that makes a difference” G. Bateson 2

3. Data: formalised, stored knowledge INFORMATION Something new, advanced interpretable knowledge  Directly with perception  From proccessing data How can you get informations? 3

4. Characteristics of Good Information relevant relevant timely timely accurate accurate targeted targeted formatted formatted reduces uncertainty reduces uncertainty 4

5. Information Systems An information system transforms data into information to help people make decisions An information system transforms data into information to help people make decisions A computer-based information system uses a computer as the technical means of carrying out the basic operations of gathering, maintaining, accessing, selecting and displaying information. A computer-based information system uses a computer as the technical means of carrying out the basic operations of gathering, maintaining, accessing, selecting and displaying information. 5

6. Basic Business Information System Order Processing Order Processing Payroll Accounts Payable Accounts Payable General Ledger General Ledger Accounts Receivable Accounts Receivable Billing Inventory Control Inventory Control Purchasing Human Resources Human Resources 6

7. Data Form: serial of signs Form: serial of signs Content:the meaning of serial of signs Content:the meaning of serial of signs Structure:the relationships between the data Structure:the relationships between the data We have to code the data. We have to code the data. 7

8. Code Who is he? DEKODE Code and Decode 8

9. Code Systems Language Language Icon Icon Digital code Digital code Bar code (Ean code) Bar code (Ean code) 9

10. Type of data Numeric (base types: Integer, real, double, spec. type: date, time…, logical Numeric (base types: Integer, real, double, spec. type: date, time…, logical Text, characters Text, characters Picture Picture Sound waves Sound waves 10

11. A Data Type together with operations defined on it. A Data Type together with operations defined on it. Useful to consider what operations are required before starting implementation. Useful to consider what operations are required before starting implementation. Data Structures: Definition 11

12. Collection data structures Very often one creates objects that hold collections of items. Very often one creates objects that hold collections of items. Each type of collection has rules for accessing the elements in it Each type of collection has rules for accessing the elements in it Array: the items are indexed by integers, and each item can be accessed according to its indexArray: the items are indexed by integers, and each item can be accessed according to its index Map (dictionary, associative array): the items are indexed by keys, and each item can be accessed according to its keyMap (dictionary, associative array): the items are indexed by keys, and each item can be accessed according to its key Queue: the items are ordered and can be accessed only in FIFO order (first in first out)Queue: the items are ordered and can be accessed only in FIFO order (first in first out) Stack: the items are ordered and can be accessed only in LIFO order (last in first out)Stack: the items are ordered and can be accessed only in LIFO order (last in first out) 12

13. Static vs. Dynamic Structures Dynamic structures: Dynamic structures: can grow and shrink during executioncan grow and shrink during execution components usually accessed via referencescomponents usually accessed via references Static structures: Static structures: fixed sizefixed size storage allocated all at oncestorage allocated all at once components are usually namedcomponents are usually named Arrays are static in old database systems; once you define the number of elements it can hold, it doesn’t change, but in modern systems they are dynamic. Arrays are static in old database systems; once you define the number of elements it can hold, it doesn’t change, but in modern systems they are dynamic. 13

14. The Most Important Data Structures according to the computer applications These are the: These are the: StackStack QueueQueue ListList 14

15. Stack A stack is linear A stack is linear Items are added and removed from only one end of a stack Items are added and removed from only one end of a stack It is therefore LIFO: Last-In, First-Out It is therefore LIFO: Last-In, First-Out Analogy: a stack of plates Analogy: a stack of platespoppush 15

16. Stack: A sequence of elements together with these operations: Initialize the stack. Initialize the stack. Determine whether the stack is empty. Determine whether the stack is empty. Determine whether the stack is full. Determine whether the stack is full. Push an item onto the top of the stack. Push an item onto the top of the stack. Pop an item off the top of the stack. Pop an item off the top of the stack. 16

17. A stack holds an ordered collection of items, items can be accessed only in first-in-last-out order Its operations are:  Create an empty stack  Push an item into the stack  Pop an item from the stack – removes (and returns) the last item that was pushed onto the stack  Check whether the stack it empty or not 17

18. Stack sample run Create empty stack { } Push 5 { 5 } Push 4 { 5 4 } Push 8 { 5 4 8 } Pop (returns 8) { 5 4 } Push 7 { 5 4 7 } Pop (returns 7) { 5 4 } Pop (returns 4) { 5 } 18

19. The use of Stack Computer Architecture Most CPUs support stacks in hardware Operating Systems Used in many aspects of implementation of high level programming languages 19

20. The using of stacks in running programs Space used as temporary storage during the execution of the program Space used as temporary storage during the execution of the program Purpose: Purpose: saving the return address when calling proceduressaving the return address when calling procedures saving the contents of registers used in proceduressaving the contents of registers used in procedures pass parameters to procedurespass parameters to procedures allocate memory for local variables in proceduresallocate memory for local variables in procedures A single access point. LIFO data structure A single access point. LIFO data structure Data is always accessed from the “top” of the stackData is always accessed from the “top” of the stack Insert is done by “pushing” data to the top of the stackInsert is done by “pushing” data to the top of the stack Delete is done by “popping” data from the top of the stackDelete is done by “popping” data from the top of the stack 20

21. Stack layout in memory In use Free Original Direction of increasing memory addresses Stack grows in direction of decreasing memory addresses 21

22. Queues A queue is similar to a list but adds items only to the end of the list and removes them from the front A queue is similar to a list but adds items only to the end of the list and removes them from the front It is called a FIFO data structure: First-In, First-Out It is called a FIFO data structure: First-In, First-Out Analogy: a line of people at a bank teller’s window Analogy: a line of people at a bank teller’s window enqueue dequeue 22

23. Queues Initialize the queue. Initialize the queue. Determine whether the queue is empty. Determine whether the queue is empty. Determine whether the queue is full. Determine whether the queue is full. Find the size of the queue. Find the size of the queue. Append an item to the rear of the queue. Append an item to the rear of the queue. Serve an item at the front of the queue. Serve an item at the front of the queue. A sequence of elements together with these operations: 23

24. Bank Teller Example Classes Classes Data structures Data structures Input Input Time step = 5 secTime step = 5 sec Transaction = 2 minutesTransaction = 2 minutes Customer Frequency = 50% chance every 15 secondsCustomer Frequency = 50% chance every 15 seconds What questions do we want to know? What questions do we want to know? Average wait timeAverage wait time Average line lengthAverage line length How a simulation would work How a simulation would work 24

25. Bank Teller Example Customer 1 – 0:00 Customer 2 – 0:15 Customer 3 – 0:30 Customer 4 – 1:15 Customer 5 – 1:30 Customer 6 – 1:45 Customer 7 – 2:15 Customer 8 – 2:45 Customer 9 – 4:00 Customer 10 – 5:30 Customer 11 – 5:45 Customer 12 – 6:15 Customer 13 – 6:30 Customer 14 – 6:45 Customer 15 – 7:30 Customer 16 – 7:45 Customer 17 – 8:15 Customer 18 – 8:30 25

26. A List Initialize the list. Initialize the list. Determine whether the list is empty. Determine whether the list is empty. Determine whether the list is full. Determine whether the list is full. Find the size of the list. Find the size of the list. Insert an item anywhere in the list. Insert an item anywhere in the list. Delete an item anywhere in a list. Delete an item anywhere in a list. Go to a particular position in a list. Go to a particular position in a list. A sequence of elements together with these operations: 26

27. Linear list A sequence of elements A sequence of elements There is first and last element There is first and last element Each element has previous and next Each element has previous and next Nothing before firstNothing before first Nothing after lastNothing after last 27

28. What makes a special kind of list What we can do with a linear list? What we can do with a linear list? Delete elementDelete element Insert elementInsert element Find elementFind element Is the list sorted or not? Is the list sorted or not? NumericallyNumerically AlphabeticallyAlphabetically Any other wayAny other way 28

29. Some classification of lists We can consider queue and stack as special type of list 29

30. Insert: list, data  new list 30

31. Retrieve: list, criteria  element 31

32. Delete: list, criteria  new list 32

33. A linked list implementation Linked list is a chain of elements Linked list is a chain of elements Each element has data part and link part pointing to the next element Each element has data part and link part pointing to the next element 33