Data and informationData and information

These are philosophical categoriesThese are philosophical categories We are not able to give exact We are not able to give exact

definitiondefinition In everyday life we use these concept In everyday life we use these concept

as synonymsas synonyms We onlyWe only have have ideasideas about these words about these words

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Definitions of InformationDefinitions of Information Information is ….Information is …. “…“….. data processed for a purpose”.. data processed for a purpose” R. CurtisR. Curtis

“…“….. knowledge derived from data”... knowledge derived from data”.

“…“….. data placed within a context”.. data placed within a context”D. KroenkeD. Kroenke

“…“….. the amount of uncertainty that is .. the amount of uncertainty that is reduced when a message is received”reduced when a message is received”

Shannon and WeaverShannon and Weaver

“…“….. a difference that makes a difference”.. a difference that makes a difference”G. BatesonG. Bateson

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Data: formalised, stored knowledge

INFORMATION

Something new, advanced

interpretableknowledge

Directly with perceptionFrom proccessing data

How can you get informations?

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Characteristics of Good Characteristics of Good InformationInformation

relevantrelevant timelytimely accurateaccurate targetedtargeted formattedformatted reduces uncertaintyreduces uncertainty

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Information SystemsInformation Systems

An information system transforms An information system transforms data into information to help data into information to help people make decisionspeople make decisions

A computer-based information A computer-based information system uses a computer as the system uses a computer as the technical means of carrying out the technical means of carrying out the basic operations of gathering, basic operations of gathering, maintaining, accessing, selecting maintaining, accessing, selecting and displaying information.and displaying information.

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Basic Business Information Basic Business Information SystemSystem

OrderProcessing

OrderProcessing

PayrollPayroll

AccountsPayable

AccountsPayable

GeneralLedger

GeneralLedger

AccountsReceivable

AccountsReceivableBillingBilling

InventoryControl

InventoryControl

PurchasingPurchasing Human Resources

Human Resources

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DataData Form: Form: sserial of signserial of signs Content:Content: the meaning of serial of signsthe meaning of serial of signs Structure:the relationships between Structure:the relationships between

the datathe data We have to code the data.We have to code the data.

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Personal Number Name ….

2 770511 621 8 Joó Bori ….2 711207 352 5 Szabó Kati ….1 690429 019 4 Vígh Géza ….1 620115 360 5 Pók Pál ….1 521026 306 9 Borz Aladár ….2 560805 153 3 Komor Jolán ….2 580918 210 9 Kancsal Panna ….1 660206 450 3 Sék Elek ….2 600620 531 6 Szabó Kati ….2 790404 234 5 Kiss Virág ….….. ………….. ….

CodeWho is he?

DEK

OD

ECode and DecodeCode and Decode

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CCodeode SystemsSystems

LanguageLanguage IconIcon Digital codeDigital code Bar code (Bar code (Ean codeEan code))

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Type of dataType of data

NumericNumeric(base types: Integer, real, double,(base types: Integer, real, double,specspec.. type: dat type: datee, time…, logical, time…, logical

TextText, characters, characters PicturePicture Sound wSound waavesves

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A Data A Data TypeType together with operations together with operations defined on it.defined on it.

Useful to consider what operations Useful to consider what operations are required before starting are required before starting implementation.implementation.

DatDataa Structures Structures:: Definition Definition

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Collection data Collection data structuresstructures Very often one creates objects that hold collections Very often one creates objects that hold collections

of items.of items. Each type of collection has rules for accessing the Each type of collection has rules for accessing the

elements in itelements in it• Array:Array: the items are indexed by integers, and each item the items are indexed by integers, and each item

can be accessed according to its indexcan be accessed according to its index• Map (dictionary, associative array):Map (dictionary, associative array): the items are indexed the items are indexed

by keys, and each item can be accessed according to its by keys, and each item can be accessed according to its keykey

• Queue:Queue: the items are ordered and can be accessed only in the items are ordered and can be accessed only in FIFO order (first in first out)FIFO order (first in first out)

• Stack:Stack: the items are ordered and can be accessed only in the items are ordered and can be accessed only in LIFO order (last in first out)LIFO order (last in first out)

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Static vs. Dynamic StructuresStatic 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 size fixed size • storage allocated all at oncestorage allocated all at once• components are usually namedcomponents are usually named

Arrays Arrays areare static static in old database systems in old database systems; ; once you define the number of elements it can once you define the number of elements it can hold, it doesn’t changehold, it doesn’t change, but in modern , but in modern systems they are dynamic.systems they are dynamic.

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The Most ImportantThe Most Important Data Data Structures Structures according to the computer according to the computer

applicationsapplications These are the:These are the:

• StackStack• QueueQueue• ListList

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StackStack A A stackstack is linear is linear

Items are added and Items are added and removed from only removed from only one end of a stackone end of a stack

It is therefore LIFO: It is therefore LIFO: Last-In, First-OutLast-In, First-Out

Analogy: a stack of Analogy: a stack of platesplates

poppoppushpush

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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.

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•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

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Stack sample runStack 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 }

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The use of The use of StackStack

•Computer ArchitectureMost CPUs support stacks in hardware

Operating SystemsUsed in many aspects of implementation of high level programming languages

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ThThe using of e using of stackstacks in running programss in running programs

Space used as temporary storage during the Space used as temporary storage during the execution of the programexecution 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 procedures saving 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 structureA 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 Insert is done by “pushing” data to the top of the

stackstack• Delete is done by “popping” data from the top of Delete is done by “popping” data from the top of

the stackthe stack2020

Stack layout in memoryStack layout in memory

In use

In use

In use

In use

In use

In use

Free

Free

Free

Free

Original

Direction of increasing memory addresses

Stack grows in direction of decreasing memory addresses

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QueuesQueues A A queuequeue is similar to a list but adds items only to the end of the is similar to a list but adds items only to the end of the

list and removes them from the frontlist and removes them from the front

It is called a FIFO data structure: First-In, First-OutIt is called a FIFO data structure: First-In, First-Out

Analogy: a line of people at a bank teller’s windowAnalogy: a line of people at a bank teller’s window

enqueue dequeue

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QueueQueuess

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:

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Bank Teller ExampleBank Teller Example

ClassesClasses Data structuresData structures InputInput

• Time step = 5 secTime step = 5 sec• Transaction = 2 minutesTransaction = 2 minutes• Customer Frequency = 50% chance every 15 Customer Frequency = 50% chance every 15

secondsseconds 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 workHow a simulation would work2424

Bank Teller ExampleBank Teller Example

Customer 1 – Customer 1 – 0:000:00

Customer 2 – Customer 2 – 0:150:15

Customer 3 – Customer 3 – 0:300:30

Customer 4 – Customer 4 – 1:151:15

Customer 5 – Customer 5 – 1:301:30

Customer 6 – Customer 6 – 1:451:45

Customer 7 – Customer 7 – 2:152:15

Customer 8 – Customer 8 – 2:452:45

Customer 9 – Customer 9 – 4:004:00

Customer 10 – Customer 10 – 5:305:30

Customer 11 – Customer 11 – 5:455:45

Customer 12 – Customer 12 – 6:156:15

Customer 13 – Customer 13 – 6:306:30

Customer 14 – Customer 14 – 6:456:45

Customer 15 – Customer 15 – 7:307:30

Customer 16 – Customer 16 – 7:457:45

Customer 17 – Customer 17 – 8:158:15

Customer 18 – Customer 18 – 8:308:30

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A List 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:

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Linear listLinear list

A sequence of elementsA sequence of elements There is first and last elementThere is first and last element Each element has previous and nextEach element has previous and next

• Nothing before firstNothing before first• Nothing after lastNothing after last

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What makes a special kind of What makes a special kind of listlist

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

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Some classification of listsSome classification of lists

We can consider queue and stack as special type of list2929

Insert: list, data Insert: list, data new list new list

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Retrieve: list, criteria Retrieve: list, criteria elementelement

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Delete: list, criteria Delete: list, criteria new list new list

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A A linked listlinked list implementation implementation

Linked list is a chain of elementsLinked list is a chain of elements Each element has data part and Each element has data part and

link part pointing to the next link part pointing to the next elementelement

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