Transcript CIT PowerPoint presentation

CIT PowerPoint presentation
Group 4
Unit 1, Chapter 2
Basic Concept on Data
DATA AND INFORMATION
What is data?
Data consists of all sorts of unorganised and
incomprehensible facts in the form of numbers,
characters, symbols, or graphics.
What is information?
Information is processed data which is meaningful
and useful.
DATA
PROCESSING
INFORMATION
Unit 1, Chapter 2
Basic Concept on Data
DATA COLLECTION AND DATA
PREPARATION
1) By interviews, Questionnaires and Forms
2) By Observations and Measurements
3) By Experiments
– (1) Checking Data for Accuracy
– (2) Structuring Data
Unit 1, Chapter 2
Basic Concept on Data
DATA MANAGEMENT
1) Sources of Errors
–
–
–
–
–
(1) During Data Collection
(2) During Data Preparation
(3) During Data Input
(4) During Data Processing
(5) During Information Output
“Garbage-in Garbage-out” situation
Unit 1, Chapter 2
Basic Concept on Data
2) Data Control
– (1) Data Verification
Data items entered are outputted immediately or as a
batch for checking against the original source, to find
out if there are any mismatched items.
Data items are typed into a computer by two different
operators independently. A program is used to
compare these two sets of data and detects any
discrepancies.
If data verification is extensively and properly used,
then the data inputted should be identical with the
original data.
Unit 1, Chapter 2
Basic Concept on Data
(2) Data Validation
Refers to the data inputted being acceptable and reasonable.
To ensure data validity, a validation program is to check the
data inputted. This is data validation.
There are 5 Types of validation check!
Type Check
Range Check
Length Check
Reasonableness Check
Check Digit
Unit 1, Chapter 2
Basic Concept on Data
Type Check
– Type check is used to check if the data types are correct. Data are
usually divided into two types: numbers and characters.
Range Check
– Range check is used to ensure that data lie within a certain range.
Unit 1, Chapter 2
Basic Concept on Data
Length Check
– Length check is used to ensure the correct number of characters or
digits in a data item.
Reasonableness Check
– Reasonableness check tries to ensure the reasonableness of data.
Unit 1, Chapter 2
Basic Concept on Data
Check Digit
– A check digit is an extra digit at the end of a code. It is used to ensure
the correctness of the code.
Example: Identity Card Number and the International Standard Book
Number (ISBN) use check digits for validation purpose.
The Check Digit of the Hong kong Identity Card Number
The 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.
1. Each digit has a weighting of 2,3,4,5,6,7,8 starting from right to left.
D308377
| | | | | | |___> 7*2 = 14
| | | | | |_____> 7*3 = 21
| | | | |______> 3*4 = 12
| | | |________> 8*5 = 40
| | |_________> 0*6 = 0
| |___________> 3*7 = 21
|_____________> 4*8 = 32
Unit 1, Chapter 2
Basic Concept on Data
2. Calculate the “ weighted sum” of the digits of the given numbers.
7*2 = 14
7*3 = 21
3*4 = 12
8*5 = 40
0*6 = 0
3*7 = 21
+)
4*8 = 32
The weighted sum = 140
3. Divide the weighted sum by 11.
11 |140
12…...8(remainder)
Unit 1, Chapter 2
Basic Concept on Data
4. Check Digit
Check digit = 11 – remainder
= 11 – 8
= 3
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.
Therefore, a valid identity card number is D308377(3). You will find that it is exactly
“divisible” by 11, in the sense that
D 3 0 8 3 7 7 (3)
| | | | | | | |_> 3*1 = 3
| | | | | | |___> 7*2 = 14
| | | | | |_____> 7*3 = 21
| | | | |______> 3*4 = 12
| | | |________> 8*5 = 40
| | |_________> 0*6 = 0
| |___________> 3*7 = 21
|_____________> 4*8 = 32
——————————————
11 | 143
13
Unit 1, Chapter 2
Basic Concept on Data
1) REPRESENTATION OF DATA INSIDE A
COMPUTER
A. Denary, Binary and Hexadecimal Number Systems
– A number system is a system that represents numbers.
For each number system, a number is composed of one or
more digits.
– The position of each digit in the number has its place value,
and the digit value is represented by the product of the
digit and its place
– 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
called the base, and is different for different number
systems.
Unit 1, Chapter 2
Basic Concept on Data
(1) Denary Number System
We usually use the decimals or denary number system to represent a
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
formed by the combination of the digits.
Example
i.e. 419210 = 4*103 + 1*102 + 9*101 + 2*100
Unit 1, Chapter 2
Basic Concept on Data
(2) Binary Number System
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
as the denary numbers except that the base is 2 instead of 10.
Example
The binary number 11112 in expanded form is:
i.e. 11112 = 1*23 + 1*22 + 1*21 + 1*20
Unit 1, Chapter 2
Basic Concept on Data
(3) Hexadecimal Number System
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
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
the decimal numbers except that the base is 16 instead of 10.
The hexadecimal number 2C3D16 in expanded form is:
i.e. 2C3D16 = 2*163 +12*162 +3*161 +13*160
Unit 1, Chapter 2
Basic Concept on Data
2) USING BINARY DIGITS TO REPRESENT
DATA
In a computer, data are represented by binary digits
“0” and “1”. Each “0” or “1” is called a bit, short
form for binary digits. Usually, eight bits are
combined into a group called a byte to represent or
encode one character. For example, the American
Standard Code for Information Interchange (ASCII) is
the most popular coding system for characters. It
uses a byte as a code to represent each character.
END
Ho Yat Pong 4B (10)
Lai Yu Fai 4B (12)
Leonardo Capocio Neto 4B (20)