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CSC115 Introduction to Computer Programming
Zhen Jiang Dept. of Computer Science West Chester University West Chester, PA 19383
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Table of Contents Structure Selection (Decision) Loop
Array and Function
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Selection (Decision) Price is right.
Sample execution (click on this link to try)
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No Yes Condition Action 1 Action 2 Action 3
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Boolean Expression Action 1 If controlled Action 2 else controlled
Yes No Boolean Expression Action 1 If controlled Action 2 else controlled Action 3 9/19/2018
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If block if condition then action 1 (statements 1) else action 2 (statements 2) end if action 3 (statement 3)
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Legal age to have driver’s license
?
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Condition Simple condition Complex condition Format
<Value> <relational operators> <Value> Number value relational operators =, <>, <, >, <=, >= String value relational operators =, <> Complex condition And, or, not Truth table, table 4, p121
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Relational operators have lower precedence than math operators.
(7 - 1) * > 7* 5 6 * > 35 > 35 33 > 35 False Relational operators cannot be chained (unlike math operators) 2 <= x <= 10 error! 9/19/2018
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Development Process Identify two exclusive options
Implement each handling in different action parts Identify the situation (values) for option selection Make a condition so that all the situation value for option part 1 will lead to this condition true. Verify all the situation value for option part 2 will lead to this condition false, otherwise, revise the above condition!
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Multiple selection Nested if block Example: letter grade
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Comments: Nested if block for multiple section problem If then case 1
Else if then case 2 else … end if End if
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If block, extension without else
if condition then action 1 (statements 1) end if action 3 (statement 3)
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Are they different, how much?
Dim x as integer, y as integer x = text1.text y=0 if x > 3 then y =1 if x >10 then y = 2 else y = 3 End if Listbox1.Items.Add( y ) Dim x as integer, y as integer x = text1.text y=0 if x > 3 then y =1 if x > 10 then y = 2 End if else y = 3 Listbox1.Items.Add( y )
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Try 0, 4, 11 and see the results! Dim x as integer, y as integer
x = text1.text y=0 if x > 3 then y =1 if x >10 then y = 2 else y = 3 End if Listbox1.Items.Add( y ) Dim x as integer, y as integer x = text1.text y=0 if x > 3 then y =1 if x > 10 then y = 2 End if else y = 3 Listbox1.Items.Add( y )
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Try 0, 4, 11 and see a worse situation!
Dim x as integer, y as integer x = text1.text y=0 if x > 3 then y =1 if x <10 then y = 2 else y = 3 End if Listbox1.Items.Add( y ) Dim x as integer, y as integer x = text1.text y=0 if x > 3 then y =1 if x < 10 then y = 2 End if else y = 3 Listbox1.Items.Add( y )
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My point One line in wrong place Structural procedure Ex 6
Could create the program 99.99% different Structural procedure Ask yourself where (the next program segment line) the computer execution goes Before that, ask yourself if you can find the “if” for each “else” Ex 6
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Select block Select case A constant A variable An expression Is
To range Else And and or
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Loop Do while Loop do while condition statements loop statements2
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No Yes condition statements1 Action 2 Action 3
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No Yes condition Statements1 Statements2
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Other loops
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Clock
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Function and procedure
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Array
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