ICS124

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ICS124 Session 8 Structured Programming
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• 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

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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.

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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.

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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

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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

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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

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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

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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

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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

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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.

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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

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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

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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

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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

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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

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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

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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

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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.
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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?
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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?
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Structured Programming, continued
IPO Charts, continued Why is the following chart
wrong?
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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. c2 a2 b2 area 0.5 x (a x b) What
would an IPO Chart look like?
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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. c2 a2 b2 area 0.5 x (a x b) What
would an IPO Chart look like?
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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
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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.
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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.
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Structured Programming, continued
IPO Charts, continued
GrossPay-YTD
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