Zhen Jiang Dept. of Computer Science West Chester University West Chester, PA 19383 zjiang@wcupa.edu...

Zhen Jiang

Dept. of Computer Science

West Chester University

West Chester, PA 19383

zjiang@wcupa.edu

CSC141 Computer Science I

Introduction T/F selection MC selection

Selection (Decision)

Rolling a dice. Sample execution (click on this link to

try http://www.cis.temple.edu/~jiang/

dice.exe Each button in the above sample has

Selection (Decision)

Win/Lost?Yes

Double themoney

Bankrupt

No

Restart

If else statement if (test)

action 1 (statements 1) elseaction 2 (statements 2) //end if

action 3 (statement 3)

Test by boolean expression

Yes

Action 1 Action 2

No

Action 3

Boolean expression in test Simple expression

Format <Value> <relational operators> <Value>

Number value relational operators, Table 3-1, page 111 ==, !=, <, >, <=, >=

!!! Number one error: “(a=2)” instead of “(a==2)” char value (not string!) relational operators

==, != (page 118)

Complex expression &&, ||, ! (Table 3-4, page 135) Truth table

Table 3-6, page 136 Table 3-7, page 139 Table 3-8, page 141

Precedence order, table 3-10, page 142 Number range, page 142-143

Ex 6: http://www.cs.wcupa.edu/~zjiang/141_ex6.pdf

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Development of a correct decision program Grade.java

Identify two exclusive options Implement each handling in different action parts Identify the situation (values) for option selection Make an expression so that all the situation value for

option part 1 will lead to the test result (boolean value) true.

Verify all the situation value for option part 2 will lead to the test false, otherwise, revise the above expression!

Development Process

Ex 7: http://www.cs.wcupa.edu/~zjiang/141_ex7.pdf

Ex 8: http://www.cs.wcupa.edu/~zjiang/141_ex8.pdf

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If statement, Code 3-1, page 113 Relational operator ?, page 151 Multiple selection

Nested if, Code 3-4, page 127 If else if, Code 3-5, page 131

Example: letter grade

Comments: Nested if for multiple selection

problemIf

case 1Else

if case 2

else…

//end of case 2 if//End of case 1 if

Development of a correct multiple-decision program Letter grade

Ex 9http://www.cs.wcupa.edu/~zjiang/141_ex9.pdf

Switch Switch([variable]) Case [constant value]: Break (or no break), Code 3-13, 3-14,

page 155-157

Project 2 11 case If-else BMI expression simplification

Last else no if Nested if and multiple if

Avg < 90 && test1 < 90 to attend the final

Discount %, ()?