2. What is pseudocode?
List of steps written in English
Like the instructions for a recipe
Must be in the right sequence
Imagine saying “bake the cake” and then “mix it up”
3. Sample Pseudocode
Task: add two numbers
Pseudocode:
Start
Get two numbers
Get first number
Get second number
Add them
Print the answer
End
4. Pseudocode
English language constructs modeled to look like
statements available in most programming
languages
Steps presented in a structured manner
(numbered, indented, and so on)
No fixed syntax for most operations is required
Invitation to Computer
Science, Java Version, Third
Edition 4
5. Pseudocode (continued)
Less ambiguous and more readable than natural
language
Emphasis is on process, not notation
Well-understood forms allow logical reasoning
about algorithm behavior
Can be easily translated into a programming
language
Invitation to Computer Science,
Java Version, Third Edition 5
6. Sample Pseudocode
Task: add two numbers
Pseudocode:
Start
Get two numbers
Get first number
Get second number
Add them
Print the answer
End
7. What does a flowchart look like?
The pseudocode from the previous slide would look
like this as a flowchart:
Start
Print answer
Get 2 numbers
End
Add them
8. What are those funny symbols?
START/END
INPUT/OUTPUT
PROCESS
DECISION
9. What are those funny symbols?
START/END
Used at the beginning
and end of each
flowchart.
10. What are those funny symbols?
INPUT/OUTPUT
Shows when
information/data comes
into a program or is
printed out.
11. What are those funny symbols?
What are those funny symbols?
PROCESS
Used to show
calculations, storing of
data in variables, and
other “processes” that
take place within a
program.
12. What are those funny symbols?
What are those funny symbols?
DECISION
Used to show that the
program must decide Y
whether something X>7?
(usually a comparison
N
between numbers) is
true or false. YES and
NO (or T/F) branches
are usually shown.
13. Another Sample:
Calculating Age
Pseudocode:
Start
Get year DOB
Calculate age = (sysdate-DOB)
Print age
If age > 50 print OLD
End
14. Another Sample:
Start
Calculating Age
Get yr
Calc age
Flowchart
Start Print age
Get year born
Calculate age OLD Y Age>50?
Print age
N
If age > 50 print OLD End
End
15. Self-Check
Look at the flowchart section below. If the variable X is
5, what will print (K or 1st)?
Print “K” N Y Print “1st”
X > 5?
16. Self-Check
Look at the flowchart section below. If the variable X is
5, what will print (K or 1st)?
Print “K” N Y Print “1st”
X > 5?
K will be printed. The answer to the question “Is X greater than 5
is NO, since X is equal to (not greater than) 5.
17. Self-Check
Choose the correct
flowchart symbol for each
of these statements.
AGE>65?
Calc. Tax
START
Print NAME
18. Self-Check
Choose the correct
flowchart symbol for each
of these statements.
AGE>65?
Calc. Tax
START
Print NAME
19. Challenge
Try to write pseudocode and create a flowchart for a
program that calculates the average of three grades
and prints the average.
The word GOOD should be printed only if the average
is more than 80.
20. Challenge
Possible pseudocode
Start
Get three grades
Average them (add all of them / number of grads taken)
Print Average
Average>80?
If Yes, print GOOD
End
21. START
Challenge Get 3 grades
Possible flowchart
Start Calc avg
Get three grades
Average them
Print avg
Print Average
Average>80?
Y
If Yes, print GOOD GOOD Avg>80?
End
N
END
22. Challenge
Try to write pseudocode and create a flowchart for a
program that calculates the average of three grades
and prints the average.
The word GOOD should be printed only if the average
is more than 80.
23. Challenge
Possible pseudocode
Start
Get three grades
Average them
Print Average
Average>80?
If Yes, print GOOD
End
24. START
Challenge Get 3 grades
Possible flowchart
Start Calc avg
Get three grades
Average them
Print avg
Print Average
Average>80?
Y
If Yes, print GOOD GOOD Avg>80?
End
N
END
