Program Planning Part I

• Look at Some simple ice cream store problems.
  • I made these up for this exercise.
• We would eventually like to write a program to solve each of these problems.
• But let's use Dale's problem solving process.
  1. Problem Solving Phase
     1. Analysis and specification
     2. General solution
     3. Verify
  2. Implementation
  3. Maintenance
• Read the first problem.
  • Is there anything that is unclear?
  • Is there anything that is unspecified?
  • Is there anything you don't understand?
  • Can we buy partial gallons of ice cream from our supplier? No, only gallons.
  • Do we sell different sizes of ice cream cones? Not yet.
  • Do we sell different flavors of ice cream cones? Not yet.
  • If the answer to anything is YES then you need to ask for clarification.
• What does the problem ask you to do?
  • Given the number of ice cream cones to produce compute the number of gallons of ice cream needed if a gallon of ice cream will make 24 cones.
• What is the input/output
  • Input: I need to know how many cones they plan to sell.
  • Output: I need to output how many gallons of ice cream to order.
• How do I use this to compute the answer?
  • I need to understand how to do this before I can tell the computer how to do it.
  • Do the computation by hand.
  • If I sell 1 cone, I will need a gallon,
  • If I sell 2 cones, I will need a gallon,
  • If I sell 24 cones, I will need one gallon.
  • Looks like round up (cones/gallons)
  • 1/24 = .04 rounded up = 1 or one gallon.
  • 24/24 = 1 or one gallon
  • 25/24 = 1.04 rounded up = 2 or 2 gallon.
  • 259 / 24 = 10.79 or 11 gallons
• Note, in testing our procedure, we get a number of test cases

  Cones	Gallons of Ice Cream
  1	1
  2	1
  24	1
  25	2
  259	11

  • This will be useful later when we test our program.
• Write down your plan in short English sentences

  • ask the user for the number of cones
    gallons = roundup(cones/24) 
    print the number of gallons needed

• This last part is called pseudo-code or false code.
  • pseudo-code is a set of short instructions written in your native language.
  • There is no real format
    • Instructions should be short.
    • And easy to understand
    • And should correspond to a line of code.
• This algorithm is fairly strait forward, but let's trace it anyway.

  Print: How many cones do you plan to sell?
  User Input 1:
  cones: 1
  gallons: roundup(1/24) = 1
  Print: Gallon(s) needed: 1
  
  Print: How many cones do you plan to sell?
  User Input: 24
  cones: 24
  gallons: roundup(24/24) = 1
  Print: Gallon(s) needed: 1
  
  Print: How many cones do you plan to sell?
  User Input: 25
  cones: 25
  gallons: roundup(25/24) = 2
  Print: Gallon(s) needed: 2
  
  Print: How many cones do you plan to sell?
  User Input: 259
  cones: 259
  gallons: roundup(259/24) = 11
  Print: Gallon(s) needed: 11 

• A java solution to this problem is here.
  • Don't worry about it yet,
  • but can you see the similarity of the code to the algorithm.
  • The code has a lot of extra details.