pseudocode and Flowchart

pseudocode and Flowchart
lec.3

1. pseudocode and Flowchart

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. Invitation to Computer Science, Java Version, Third Edition 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

5. Invitation to Computer Science, Java Version, Third Edition 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

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 Get 2 numbers Add them Print answer End

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. INPUT/OUTPUT Shows when information/data comes into a program or is printed out. What are those funny symbols?

11. What are those funny symbols? PROCESS Used to show calculations, storing of data in variables, and other “processes” that take place within a program. What are those funny symbols?

12. What are those funny symbols? DECISION Used to show that the program must decide whether something (usually a comparison between numbers) is true or false. YES and NO (or T/F) branches are usually shown. What are those funny symbols? Y N X>7?

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: Calculating Age Flowchart  Start Get year born Calculate age Print age If age > 50 print OLD End Get yr Calc age Print age Age>50? OLD Y N Start End

15. Self-Check Look at the flowchart section below. If the variable X is 5, what will print (K or 1st)? X > 5? Y N Print “1st” Print “K”

16. Self-Check Look at the flowchart section below. If the variable X is 5, what will print (K or 1st)? X > 5? Y N Print “1st” Print “K” 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. Challenge Possible flowchart  Start Get three grades Average them Print Average Average>80? If Yes, print GOOD End START END Get 3 grades Calc avg Print avg Avg>80? GOOD Y N

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. Challenge Possible flowchart  Start Get three grades Average them Print Average Average>80? If Yes, print GOOD End START END Get 3 grades Calc avg Print avg Avg>80? GOOD Y N

25. Algorithm for Computing Average Miles per Gallon

26. Write a program to do the task: Print a list of the numbers from 4 to 9, next to each number, print the square of the number.