1. CSC141 Computer Science I Zhen Jiang Dept. of Computer Science
West Chester University
West Chester, PA 19383

2. Selection (Decision)
Introduction
T/F selection
MC selection

3. Selection (Decision) Rolling a dice.
Sample execution (click on this link to try
Each button in the above sample has

4. No
Yes
Win/Lost?
Double the
money
Bankrupt
Restart

5. If else statement
if (test)
action 1 (statements 1)
else
action 2 (statements 2)
//end if
action 3 (statement 3)

6. No
Yes
Test by
boolean expression
Action 1
Action 2
Action 3

7. Boolean expression in test
Simple expression
Format
<Value> <relational operators> <Value>
Number value relational operators, Table 3-1, page 113
==, !=, <, >, <=, >=
!!! Number one error: “(a=2)” instead of “(a==2)”
char value (not string!) relational operators
==, != (page 121)

8. Complex expression &&, ||, ! (Table 3-4, page 137) Truth table
Precedence order, table 3-10, page 144
Number range, page

9. Ex 6: http://www.cs.wcupa.edu/~zjiang/141_ex6.pdf
11/27/2018

10. Development of a correct decision program
Grade.java

11. Development Process 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!

12. 60, 61, 62, …, 100 ?
1, 2, …, 58, 59

13. Ex 7: http://www.cs.wcupa.edu/~zjiang/141_ex7.pdf
11/27/2018

14. If statement, Code 3-1, page 115 Relational operator ?, page 152
Multiple selection
Nested if, Code 3-4, page 129
If else if, Code 3-5, page 133
Example: letter grade

15. Comments: Nested if for multiple selection problem If case 1 Else if…
//end of case 2 if
//End of case 1 if

16. Development of a correct multiple-decision program
Letter grade

18. Ex 9

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

20. Project 2 11 case If-else BMI expression simplification Discount
Last else no if
Nested if and multiple if
Avg < 90 && test1 < 90 to attend the final
Discount
%, ()?