cit powerpoint presentation group 4. unit 1, chapter 2 basic concept on data data and information...

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Unit 1, Chapter 2Unit 1, Chapter 2Basic Concept on DataBasic Concept on Data

DATA AND INFORMATIONDATA AND INFORMATIONWhat is data? What is data? Data consists of all sorts of unorganised and Data consists of all sorts of unorganised and incomprehensible facts in the form of numbers, incomprehensible facts in the form of numbers, characters, symbols, or graphics.characters, symbols, or graphics.What is information?What is information?Information is processed data which is meaningful Information is processed data which is meaningful and useful.and useful.

DATA DATA PROCESSING INFORMATION PROCESSING INFORMATION


DATA COLLECTION AND DATA DATA COLLECTION AND DATA PREPARATIONPREPARATION

1) By interviews, Questionnaires and Forms1) By interviews, Questionnaires and Forms

2) By Observations and Measurements2) By Observations and Measurements

3) By Experiments3) By Experiments

– (1) Checking Data for Accuracy(1) Checking Data for Accuracy

– (2) Structuring Data(2) Structuring Data


DATA MANAGEMENTDATA MANAGEMENT

1) Sources of Errors1) Sources of Errors– (1) During Data Collection(1) During Data Collection

– (2) During Data Preparation(2) During Data Preparation

– (3) During Data Input(3) During Data Input

– (4) During Data Processing(4) During Data Processing

– (5) During Information Output(5) During Information Output““Garbage-in Garbage-out” situationGarbage-in Garbage-out” situation


2) Data Control2) Data Control– (1) Data Verification(1) Data Verification

Data items entered are outputted immediately or as a Data items entered are outputted immediately or as a batch for checking against the original source, to find batch for checking against the original source, to find out if there are any mismatched items.out if there are any mismatched items.Data items are typed into a computer by two different Data items are typed into a computer by two different operators independently. A program is used to operators independently. A program is used to compare these two sets of data and detects any compare these two sets of data and detects any discrepancies. discrepancies. If data verification is extensively and properly used, If data verification is extensively and properly used, then the data inputted should be identical with the then the data inputted should be identical with the original data.original data.


(2) Data Validation(2) Data ValidationRefers to the data inputted being acceptable and reasonable. Refers to the data inputted being acceptable and reasonable.

To ensure data validity, a validation program is to check the To ensure data validity, a validation program is to check the data inputted. This is data validation.data inputted. This is data validation.

There are 5 Types of validation check!There are 5 Types of validation check!Type CheckType Check

Range CheckRange Check

Length CheckLength Check

Reasonableness CheckReasonableness Check

Check DigitCheck Digit


Type CheckType Check– Type check is used to check if the data types are correct. Data are Type check is used to check if the data types are correct. Data are

usually divided into two types: numbers and characters.usually divided into two types: numbers and characters.

Range CheckRange Check– Range check is used to ensure that data lie within a certain range.Range check is used to ensure that data lie within a certain range.


Length CheckLength Check– Length check is used to ensure the correct number of characters or Length check is used to ensure the correct number of characters or

digits in a data item.digits in a data item.

Reasonableness CheckReasonableness Check– Reasonableness check tries to ensure the reasonableness of data.Reasonableness check tries to ensure the reasonableness of data.


Check DigitCheck Digit– A check digit is an extra digit at the end of a code. It is used to ensure tA check digit is an extra digit at the end of a code. It is used to ensure t

he correctness of the code.he correctness of the code.Example: Identity Card Number and the International Standard Book NumbeExample: Identity Card Number and the International Standard Book Number (ISBN) use check digits for validation purpose.r (ISBN) use check digits for validation purpose.The Check Digit of the Hong kong Identity Card NumberThe Check Digit of the Hong kong Identity Card NumberThe following is an illustraion on how to find the check digit of an identity carThe following is an illustraion on how to find the check digit of an identity card number, e.g. D308377(?), when the other digits are known.d number, e.g. D308377(?), when the other digits are known.1. Each digit has a weighting of 2,3,4,5,6,7,8 starting from right to left.1. Each digit has a weighting of 2,3,4,5,6,7,8 starting from right to left.D 3 0 8 3 7 7D 3 0 8 3 7 7| | | | | | |___> 7*2 = 14| | | | | | |___> 7*2 = 14| | | | | |_____> 7*3 = 21| | | | | |_____> 7*3 = 21| | | | |______> 3*4 = 12| | | | |______> 3*4 = 12| | | |________> 8*5 = 40| | | |________> 8*5 = 40| | |_________> 0*6 = 0| | |_________> 0*6 = 0

| |___________> 3*7 = 21| |___________> 3*7 = 21 |_____________> 4*8 = 32|_____________> 4*8 = 32


2.2. Calculate the “ weighted sum” of the digits of the given numbers.Calculate the “ weighted sum” of the digits of the given numbers.

7*2 = 147*2 = 14

7*3 = 217*3 = 213*4 = 123*4 = 128*5 = 408*5 = 400*6 = 00*6 = 03*7 = 213*7 = 21

+) +) 4*8 = 32 4*8 = 32 The weighted sumThe weighted sum = 140 = 140

3. Divide the weighted sum by 11.3. Divide the weighted sum by 11.11 11 |140|140

12…...8(remainder)12…...8(remainder)


4. 4. Check DigitCheck Digit Check digit = 11 – remainderCheck digit = 11 – remainder

= 11 – 8 = 11 – 8 = 3= 3

Note that if the remainder is 0, the check digit is 0. If the remainder is 1, the check digit Note that if the remainder is 0, the check digit is 0. If the remainder is 1, the check digit is 10 and a letter “A” is used.is 10 and a letter “A” is used.

Therefore, a valid identity card number is D308377(3). You will find that it is exactly Therefore, a valid identity card number is D308377(3). You will find that it is exactly “divisible” by 11, in the sense that“divisible” by 11, in the sense that

D 3 0 8 3 7 7 (3)D 3 0 8 3 7 7 (3) | | | | | | | |_> 3*1 = 3| | | | | | | |_> 3*1 = 3 | | | | | | |___> 7*2 = 14| | | | | | |___> 7*2 = 14 | | | | | |_____> 7*3 = 21| | | | | |_____> 7*3 = 21 | | | | |______> 3*4 = 12| | | | |______> 3*4 = 12 | | | |________> 8*5 = 40| | | |________> 8*5 = 40 | | |_________> 0*6 = 0| | |_________> 0*6 = 0 | |___________> 3*7 = 21| |___________> 3*7 = 21 |_____________> 4*8 = 32|_____________> 4*8 = 32————————————————————————————

11 11 | 143| 143 1313


1) REPRESENTATION OF DATA INSIDE A 1) REPRESENTATION OF DATA INSIDE A COMPUTERCOMPUTERA. Denary, Binary and Hexadecimal Number SystemsA. Denary, Binary and Hexadecimal Number Systems– A number system is a system that represents numbers. A number system is a system that represents numbers.

For each number system, a number is composed of one or For each number system, a number is composed of one or more digits. more digits.

– The position of each digit in the number has its place The position of each digit in the number has its place value, and the digit value is represented by the product of value, and the digit value is represented by the product of the digit and its placethe digit and its place

– It must be noted that the place value of each digit is larger It must be noted that the place value of each digit is larger than that of the following digit by a factor. This factor is than that of the following digit by a factor. This factor is called the base, and is different for different number called the base, and is different for different number systems.systems.


(1) Denary Number System(1) Denary Number System

We usually use the decimals or denary number system to represent a We usually use the decimals or denary number system to represent a number. The denary number system uses ten digits to represent number. The denary number system uses ten digits to represent numbers: 0,1,2,3,4,5,6,7,8,9 and use 10 as its base. A number is numbers: 0,1,2,3,4,5,6,7,8,9 and use 10 as its base. A number is

formed by the combination of the digits.formed by the combination of the digits. ExampleExample

i.e. 4192i.e. 41921010 = 4*10 = 4*1033 + 1*10 + 1*1022 + 9*10 + 9*1011 + 2*10 + 2*1000


(2) Binary Number System(2) Binary Number SystemIn the binary number system, only digits 0 and 1 are used. It is base-2 In the binary number system, only digits 0 and 1 are used. It is base-2 number system. The binary numbers are constructed in the same way number system. The binary numbers are constructed in the same way as the denary numbers except that the base is 2 instead of 10.as the denary numbers except that the base is 2 instead of 10.

ExampleExample

The binary number 1111The binary number 111122 in expanded form is: in expanded form is:

i.e. 1111i.e. 111122 = 1*2 = 1*233 + 1*2 + 1*222 + 1*2 + 1*211 + 1*2 + 1*200


(3) Hexadecimal Number System(3) Hexadecimal Number SystemIn the hexadecimal number system, the digits In the hexadecimal number system, the digits 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E and F are used. (A,B,C,D,E and F 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E and F are used. (A,B,C,D,E and F represent 10,11,12,13,14,15 respectively.) It is a base-16 number represent 10,11,12,13,14,15 respectively.) It is a base-16 number system. The hexadecimal number are constructed in the same way as system. The hexadecimal number are constructed in the same way as the decimal numbers except that the base is 16 instead of 10.the decimal numbers except that the base is 16 instead of 10.

The hexadecimal number 2C3DThe hexadecimal number 2C3D1616 in expanded form is: in expanded form is:

i.e. 2C3Di.e. 2C3D1616 = 2*16 = 2*1633 +12*16 +12*1622 +3*16 +3*1611 +13*16 +13*1600


2) USING BINARY DIGITS TO REPRESENT 2) USING BINARY DIGITS TO REPRESENT DATADATAIn a computer, data are represented by binary digits In a computer, data are represented by binary digits “0” and “1”. Each “0” or “1” is called a bit, short “0” and “1”. Each “0” or “1” is called a bit, short form for binary digits. Usually, eight bits are form for binary digits. Usually, eight bits are combined into a group called a byte to represent or combined into a group called a byte to represent or encode one character. For example, the American encode one character. For example, the American Standard Code for Information Interchange (ASCII) is Standard Code for Information Interchange (ASCII) is the most popular coding system for characters. It the most popular coding system for characters. It uses a byte as a code to represent each character. uses a byte as a code to represent each character.

ENDENDHo Yat Pong 4B (10)Ho Yat Pong 4B (10)

Lai Yu Fai 4B (12)Lai Yu Fai 4B (12)

Leonardo Capocio Neto 4B (20)Leonardo Capocio Neto 4B (20)

cit powerpoint presentation group 4. unit 1, chapter 2 basic concept on data data and information...

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