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? 2 ? : ??????? Basic Concepts on Data

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2 : Basic Concepts on Data S.4-5 CS&IT CE Course Data and Information ... – PowerPoint PPT presentation

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Title: ? 2 ? : ??????? Basic Concepts on Data


1
? 2 ? ??????? Basic Concepts on
Data
S.4-5 CSIT CE Course ????????????????
2
????? Data and Information
  • ?? Data
  • ????????????????? Consists of all sorts of
    unorganised and meaningless facts
  • ??????????? numbers, characters or graphics

3
????? Data and Information
  • ??Information
  • ?????????????????? Is processed data which is
    meaningful and useful

4
????? Data and Information
  • ???????????????,??????
  • The process of converting raw data into
    meaningful information is known as data processing

?? Data
?? Processing
?? Information
5
???????Data Collection and Data
????????????? Data can be obtained in different
ways
  • By interviews, questionnaires and forms
  • ????????

6
  • 2. ?????
  • By Observations and Measurements

7
3. ?? By Experiments
8
???????? Data Collection and Data
  • ????????
  • Checking data for accuracy
  • ????
  • Structuring data

9
???????? Checking data for accuracy
  • ???????????????,??????????????
  • eg. a filled-out questionnaire needs to be
    edited for missed-out data, spelling or
    grammatical mistakes

10
???? Structuring data
  • ???????????????? Rearranging data in a form that
    facilitates data input

11
???? Data Management
  • ????? Sources of Errors
  • ?????? During data collection
  • ?????? During data preparation
  • ?????? During data input
  • ?????? During data processing
  • ?????? During information output

12
????? Sources of Errors
  1. ?????? During data collection

13
????? Sources of Errors
  1. ?????? During data preparation

???????????,??????8??????3? Eg. writing a 3
for an 8when preparing an edited version of the
source document
14
????? Sources of Errors
  1. ?????? During data input

?????,??????????????????,?????? When data are
inputted into a computer, errors may occur if the
operator makes typing mistakes, misread or even
leaves out the data
15
????? Sources of Errors
  • ?????? During data processing

????????????? May come from incorrect programs or
procedures
16
????? Sources of Errors
  1. ?????? During information output

??????????? May be produced by a defective output
device
17
???? Data Control
??????????????????????? Data control refers to
the measures to ensure that the data inputted is
accurate and complete
18
???? Data Control
  • ???? Data verification
  • ??????? Data validation

19
????Data Verification
  • ??????????????????
  • Checking of the truth or accuracy of data

20
????Data Verification
  • ??????????,??????????? Data items entered are
    outputted immediately for checking

21
????Data Verification
  • ????????????????? Data items are typed into a
    computer by two different operators independently

22
??????? Data Validation
  • ???????????????????
  • Refers to the data inputted being acceptable and
    reasonable

23
?????????? Type of Data validation
  1. ???? Type check
  2. ???? Range check
  3. ???? Length check
  4. ????? Reasonableness check
  5. ????Check Digit

24
???? Type Check
  • ?????????????????
  • e.g. examination marks should be numbers but not
    alphabets

25
???? Range Check
  • ????????? 1 ? 31 ??
  • e.g. the number of days in January should be
    within 1 31

26
  • ???? Length Check
  • ????????????? 8 ???????
  • A telephone number in Hong Kong has 8 digits

27
???? Reasonableness Check
  • ???? 200 ??? 5 ?????????
  • e.g. a 5-year-old child having a weight of 200
    kg is incredible

28
???? Check Digit
  • ????????????????,??????????????????? An extra
    digit at the end of a code, e.g. Identity Card
    Number, International Standard Book Number (ISBN)

29
???????????Representation of Data inside a
Computer
?????????????? Denary, Binary and Hexadecimal
Number Systems
  • ????? Denary number system
  • ?0?1?2?3?4?5?6?7?8?9
  • ???? 419210 ?????

? 419210 4103 1102 9101 2100
30
  • ????? Denary Number System
  • ????? 0.21310 ?????

? 0.21310 210-1 110-2 310-3
31
  • ????? Binary Number System
  • ?? 0 ? 1 ???????? only digits 0 and 1 are used
  • ??????2 a base-2 number system
  • ???? 11112 ????? a binary number 11112 in
    expanded form is

? 11112 123 122 121 120
32
?????? Binary Fraction Number System
  • ????? 0.10112 ?????
  • a binary fraction 0.10112 in expanded form is

? 0.10112 12-1 02-2 12-3 12-4
33
  • ??????
  • Hexadecimal Number System

0?1?2?3?4?5?6?7?8?9?A?B?C?D?E?F A 10 B 11 C
12 D 13 E 14 F 15
34
  • ??????
  • Hexadecimal Number System
  • ????? 2C3D16 ?????
  • Hex. number 2C3D16 in expanded form is

? 2C3D16 2163 C162 3161 D160
35
??????????? Using Binary Digits to Represent Data
  • ????,?????????0???1???
  • In a computer, data are represented by binary
    digits 0 and 1
  • ????????? American Standard Code for Information
    Interchange (ASCII)
  • ???????????? the most popular coding system for
    characters
  • ????????????????? uses a byte as a code to
    represent each character

36
??????????? Using Binary Digits to Represent Data
  • ???????,?????????16??????
  • To represent Chinese characters, each Chinese
    character is assigned a 16 bits internal code

37
?? Classwork
  • P.29 MC Q.1-7
  • P.31 Q.5, 6

38
?? Homework
  • P.30 Q.1-4, 7
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