1. CSC115 Introduction to Computer Programming
Zhen Jiang
Dept. of Computer Science
West Chester University
West Chester, PA 19383

2. Table of Contents Structure Selection (Decision) Loop
Array and Function

3. Selection (Decision) Price is right.
Sample execution (click on this link to try)

4. No
Yes
Condition
Action 1
Action 2
Action 3

5. 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

6. If block
if condition then
action 1 (statements 1)
else
action 2 (statements 2)
end if
action 3 (statement 3)

7. Legal age to have driver’s license?

8. 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

9. 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

10. 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!

12. Multiple selection
Nested if block
Example: letter grade

13. Comments: Nested if block for multiple section problem If then case 1
Else
if then
case 2
else …
end if
End if

14. If block, extension without else
if condition then
action 1 (statements 1)
end if
action 3 (statement 3)

15. 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 )

16. 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 )

17. 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 )

18. 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

19. Select block Select case A constant A variable An expression Is
To range
Else
And and or

20. Loop
Do while Loop
do while condition
statements
loop
statements2

21. No
Yes
condition
statements1
Action 2
Action 3

22. No
Yes
condition
Statements1
Statements2

23. Other loops

24. Clock

25. Function and procedure

26. Array