Post on 16-Dec-2015
transcript
COM148X1Interactive Programming
Lecture 5
Topics Today
Flowchart Pseudo-Code Design Approach Array Collection
Flowchart
What is Flowchart
Flowchart is used to represent the design of the program flow
There are commonly 5 symbols used in flowchart, symbols in flowchart are connected by arrows terminal input/ output process decision connector
Terminal used to represent the start/ end of the program
Input/ Output
Process
Decision
Connector used to connect different parts of flowchart when the direct
connection among these parts are messy
Flowchart Symbols
Flowchart Example
salary =salary + 300
Start
working year > 3?
Enter working year
End
Enter salary
Output salary
yes
no
Output“bonus avail.”
A
B
BA
Pseudo-Code
Pseudo-Code
Pseudo-Code is tools other than flowchart to represent the design of program flow
Pseudo-Code looks like mixture of program code and human language (mostly English)
Pseudo-Code Example
BeginRead working year from userRead salary from userIf working year > 3 then
salary ← salary + 300Output “Bonus Available”
End ifOutput salary
End
Design Approach
Limitation of Flowchart and Pseudo-Code
Both flowchart and pseudo-code become less usable when the program logic becomes too complicated
Large program project required programmers to break down the tasks into small pieces until the tasks is simple enough to handle
There are two approaches Top-down approach Bottom-up approach
Top-down Approach
In top down approach, a task will be divided into different smaller tasks. If the smaller tasks’ complexity is still high, the smaller tasks will be further divided until all tasks are manageable
Top-down Approach
Calculate the Net-Profit
Calculate the Cost Calculate the Gain
Calculate Workers Salary
Calculate Tax
Calculate Insurance
direction of breakdown
Bottom-up Approach
Unlike top-down approach, bottom-up approach try to search any manageable tasks which can be use to accomplished the main tasks. Then compose all of them to become the main task
Bottom-up Approach
Calculate the Net-Profit
Calculate the Cost Calculate the Gain
Calculate Workers Salary
Calculate Tax
Calculate Insurance
direction of compose
Array
What is Array
Array is a collection of data of same type Size of array is fixed unless it is being asked
to change Array is random access Index of array start from 0
Declare Array
Dim array_name(max_index) As data_type
Example Dim a(5) As Integer
0
a
0
0
1
0
2
0
3
0
4
0
5
Access Array Data
array_name( index ) Example
a(3) = 10 ‘write array Dim b As Integer = a(3) ‘read array
a
10
b
0
0
0
1
0
2
10
3
0
4
0
5
UBound Function
Obtain the largest index of an array Example
For j = 0 To UBound(a)a(i) = 20
Next j
20
a
0
20
1
20
2
20
3
20
4
20
5
Resize an Array
Redim array_name(max_index) Redim Preserve array_name(max_index) If keyword Preserve is used, the data in origi
nal array will be copied to the new array as long as the new array can hold
Redim Example 1
Redim a(3)
60
a
0
44
1
81
2
72
3
90
4
9
5
Before Redim
0
a
0
0
1
0
2
0
3
After Redim
Redim Example 2
Redim Preserve a(3)
60
a
0
44
1
81
2
72
3
90
4
9
5
Before Redim
60
a
0
44
1
81
2
72
3
After Redim
Multi-Dimension Array
Multi-Dimension Array is the array using multiple index for data access
Dim array_name(max_index1, max_index2, …) As data_type
Multi-Dimension Array Example
Dim b(1, 5) As Integerb(1, 3) = 13b(0, 5) = 27Dim i As Integer = UBound(b, 1) ‘i = 1Dim j As Integer = UBound(b, 2) ‘j = 5
0
b
0
0
1
0
2
13
3
0
4
0
5
0 0 0 0 0 270
1
Collection
What is Collection
Collection is a group of data which can be retrieved either by index or string
Collection index started from 1 Dim collection_name As New Collection()
Example Dim marks As New Collection()
Access Data in Collection
Add data to Collection collection.Add(data, key) marks.Add(10,”Jackson”)
Retrieve data from Collection
collection(key)collection(index)
x = marks(“Jackson”)x = marks(0)
Remove data from Collection
collection.Remove(key)collection.Remove(index)
marks.Remove(“Jackson”)marks.Remove(0)
Count number of data in Collection
collection.Count() cnt = marks.Count()