1. ICS124 Session 8 Structured Programming 1

2. By the end of this section the student will be able to:  List the steps of a model Systems Development Life Cycle  Describe the purpose of each of the model steps  List the steps of a model Program Development Cycle  Describe the purpose of each step of the Program Development Cycle  Name which columns of an IPO Chart contain verbs and which contain nouns  Represent a word problem in an IPO Chart 2

3. Structured Programming Background As systems become more complex, and businesses become more reliant on computers, means to structure the way new software is delivered is needed. There are two aspects that will be discussed:  System Development Life Cycle  Program Development Cycle The Program Development Cycle is a subset of the System Development Life Cycle. The following slides will provide an overview of SDLC and PDC. The section on PDC will be investigated closer for the remainder of the course. 3

4. Structured Programming, continued System Development Life Cycle The steps of the System Development Life Cycle are:  Analyze System  Define System Requirements  Design New System  Develop New System  Accept New System  Implement System These steps are guidelines, and are not cast in stone. Each company will have some variation of these steps. There may be more steps, or some steps will be combined. 4

5. Structured Programming, continued SDLC: Analyze System  Performed on existing manual systems as well as existing automated systems  Performed by System Analyst  Most effectively performed by interviewing the users  Identify what is done, and how  Identify any problems with current system  Go-NoGo Decision based on ROI estimates 5

6. Structured Programming, continued SDLC: Define System Requirements  What changes are required  System Analyst works with Business Analyst  Develop 'look and feel' of new system  Determine what needs to be done (not how)  Every input, output and process is documented:  Output: reports, screen designs  Input:what data, where does it come from  Process:what activities are required to produce the output  Go-NoGo Decision 6

7. Structured Programming, continued SDLC: Design New System  Define all programs, files, databases, manual processes  System Flowcharts are a common tool  Like a program flowchart  Major inputs  Major outputs  Inter-relationships between entities in system  No details as to how the programs work 7

8. Structured Programming, continued SDLC: Develop New System  Involves designing, coding and unit-testing  Uses Program Development Cycle  Goal is high-quality well structured programs  Main focus of the remainder of this course 8

9. Structured Programming, continued SDLC: Accept New System  Performed by Business user or Representative who has intimate knowledge of Business functionality of the system  Entire system is tested to ensure it conforms to the System Requirements (Phase 2)  Assumes no knowledge of internal workings of system  System documentation reviewed  Implementation strategies discussed  Users trained 9

10. Structured Programming, continued SDLC: Implement New System  When the new system is implemented into the production environment  Evaluation of new system (comparison between the expected objectives and the actual results)  Results of the evaluation may become the input to a subsequent SDLC 10

11. Structured Programming, continued Program Development Cycle The steps of the Program Development Cycle are:  Define the Problem  Outline the Solution  Develop the Solution into an Algorithm  Test the Algorithm for Correctness  Code the Program into a Specific Language (C)  Run the Program on the Computer  Document and Maintain the Program These steps are guidelines, and are not cast in stone. Each company will have some variation of these steps. There may be more steps, or some steps will be combined. 11

12. Structured Programming, continued PDC: Define the Problem  Must have a clear understanding of the problem  There is no room for assumptions  There is no difference between solving the wrong problem correctly and solving the right problem incorrectly  To help with analysis, the problem should be broken into:  Inputs  Outputs  Processes  IPO Charts to be discussed later today 12

13. Structured Programming, continued PDC: Outline the Solution  Break problem into smaller tasks or steps  Create a rough draft of the solution, may include  Major processing steps  Major sub-tasks (if any)  Major control structures (repetition loops)  Major variables and record structures  Mainline logic of the program  Top-down design  Modularity and Hierarchy charts are tools discussed outside of this class 13

14. Structured Programming, continued PDC: Develop the Outline into an Algorithm  Computers cannot devise a plan or decide to act  Computers can only do what they are told, exactly the way they are told  Computers do what you tell them to do, not what you want them to do  An algorithm is a set of precise instructions which describe the task to be performed and the order in which they are to be carried out’  Flowcharts and Pseudocode to be discussed next week 14

15. Structured Programming, continued PDC: Test the Algorithm for Correctness  One of the most important steps  Identifies major logic errors  Walkthroughs are a technique for testing  Test plans are outside the scope of this class 15

16. Structured Programming, continued PDC: Code the Program  Performed only after previous design considerations have been complete  In this course the C language will be used, although these techniques can be used for any language (Fortran, COBOL, BASIC, Pascal, Turing, TAL...)  Unfortunately, this is where many people begin PDC or SDLC 16

17. Structured Programming, continued PDC: Run the Program  Most will find this the most rewarding step  This step involves the compiler, which will identify syntax errors and some basic coding/logic errors  Further testing takes place against a Test Plan  Can be very frustrating if the design and testing is incomplete before the coding is performed  May need to be performed several times 17

18. Structured Programming, continued PDC: Document and Maintain Program  Documentation is an ongoing task throughout the PDC  External Documentation  Internal Documentation  Maintenance takes place during the life of the program, due to:  Enhancements (new functionality, new requirements)  Bugs 18

19. Structured Programming, continued IPO Charts Step 1 of the Program Development Cycle referred to a tool called an IPO Chart. It is also known as a Defining Diagram. IPO is an acronym for Input Process Output. It is a technique to break a problem down into one of these three categories using a chart such as: The entries in the Input and Output columns are nouns. A distinct, singular item. The entries in the Process column are verbs. A specific, singular action. There are cases when the input and output processes can be summarized into one process statement. 19

20. Structured Programming, continued IPO Charts, continued Example: Develop a program to accept three numbers, add them together, then print their total and average. What would an IPO Chart look like? 20

21. Structured Programming, continued IPO Charts, continued Example: Develop a program to accept three numbers, add them together, then print their total and average. What would an IPO Chart look like? 21

22. Structured Programming, continued IPO Charts, continued Why is the following chart wrong? 22

23. Structured Programming, continued IPO Charts, continued Example: Develop a program that displays the area and perimeter of a triangle when only two sides are given. The two sides will be 'a' and 'b' from the diagram below. c 2 = a 2 + b 2 area = 0.5 x (a x b) What would an IPO Chart look like? a b c 23

24. Structured Programming, continued IPO Charts, continued Example: Develop a program that displays the area and perimeter of a triangle when only two sides are given. The two sides will be 'a' and 'b' from the diagram below. c 2 = a 2 + b 2 area = 0.5 x (a x b) What would an IPO Chart look like? 24

25. Structured Programming, continued IPO Charts, continued Example: In order to determine the maximum range available to an aircraft flying a specific direction, the fuel on board becomes the limiting factor. While flying the assigned heading, the aircraft may experience a headwind or a tailwind. Headwinds will be indicated by negative numbers, tailwinds by positive numbers. The cruise performance chart for the aircraft provides the airspeed and rate of fuel consumption for various altitudes and power settings. The pilot is responsible for selecting the altitude & power setting from the performance chart. Based on the values selected by the pilot from the cruise performance chart, calculate and display the actual speed of the aircraft over the ground and the maximum range of the aircraft. For maximum range, the aircraft is permitted to expend all but 15% of the starting fuel capacity. Ground speed = Cruise airspeed + wind Time aloft = (0.85 * fuel) / rate of consumption Maximum range = Ground Speed * Time aloft 25

26. Structured Programming, continued IPO Charts, continued Example: In order to determine the maximum range available to an aircraft flying a specific direction, the fuel on board becomes the limiting factor. While flying the assigned heading, the aircraft may experience a headwind or a tailwind. Headwinds will be indicated by negative numbers, tailwinds by positive numbers. The cruise performance chart for the aircraft provides the airspeed and rate of fuel consumption for various altitudes and power settings. The pilot is responsible for selecting the altitude & power setting from the performance chart. Based on the values selected by the pilot from the cruise performance chart, calculate and display the actual speed of the aircraft over the ground and the maximum range of the aircraft. For maximum range, the aircraft is permitted to expend all but 15% of the starting fuel capacity. 26

27. Structured Programming, continued IPO Charts, continued Example: Calculate the gross pay and net pay for an employee. Display each deduction, total deduction, gross pay and net pay for the employee. Overtime is calculated at 1.5 times the normal rate for hours worked in excess of 44 hours/week. Long term benefits are charged at $2.00 per every full $100.00 of gross weekly earnings to a maximum payment of $100.00 per week. Unemployment insurance is 1.3% of gross pay to a maximum of $11.40 per week. Canada Pension Plan is 1.6% of gross pay on all earnings below $700 per week. Federal tax is calculated at 17% on the first $20,000 earned annually, 23% on the next $20,000 earned annually and 29% on the remainder. Provincial tax which is calculated with the Federal tax is 49% of Federal tax collected. 27

28. Structured Programming, continued IPO Charts, continued 28 GrossPay-YTD