Programming fundamentals lecture 3

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Programming fundamentals lecture 3

  1. 1. MCS 1Tariq Ali
  2. 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. 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. 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 requiredInvitation to ComputerScience, Java Version, ThirdEdition 4
  5. 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 languageInvitation to Computer Science,Java Version, Third Edition 5
  6. 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. 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. 8. What are those funny symbols? START/END INPUT/OUTPUT PROCESS DECISION
  9. 9. What are those funny symbols?  START/END  Used at the beginning and end of each flowchart.
  10. 10. What are those funny symbols? INPUT/OUTPUT Shows when information/data comes into a program or is printed out.
  11. 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. 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. 13. Another Sample:Calculating Age Pseudocode:  Start  Get year DOB  Calculate age = (sysdate-DOB)  Print age  If age > 50 print OLD  End
  14. 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. 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. 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 5is NO, since X is equal to (not greater than) 5.
  17. 17. Self-Check  Choose the correct flowchart symbol for each of these statements.  AGE>65?  Calc. Tax  START  Print NAME
  18. 18. Self-Check  Choose the correct flowchart symbol for each of these statements.  AGE>65?  Calc. Tax  START  Print NAME
  19. 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. 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. 21. STARTChallenge 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. 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. 23. Challenge Possible pseudocode  Start  Get three grades  Average them  Print Average  Average>80?  If Yes, print GOOD  End
  24. 24. STARTChallenge 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
  25. 25.  Algorithm for Computing Average Miles per Gallon
  26. 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.

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