PE Problem Development Steps

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La Trobe University
Computer Science & Computer Engineering
Computer Science & Computer Engineering CSE1PE
Geoff Holt

La Trobe University CSE1PE: Programming Environment Understanding the Program Development Steps In CSE1PE, the following steps are very efficiently and proactively used so it’s important to read the following and pay close attention to each detail. Step 1: Define the Problem In order to continue on with a program development, you need a clear vision and to understand what is going to happen with your program. This takes the form of a ‘visual representation’. Basically, it’s a diagram which represents the flow of processing from the input, to the output. Figure 1.1: A sample visual diagram of a basic shop purchase. Output: Inputs: Change is calculated by deducting the price of price price cash the item (price) from cash the cash supplied. change In the left box, we have our inputs. If we go into a shop to purchase an item. We have two things that we need to assume. The price of the item, and the cash we will give to the attendant. We know this, but we want to know the change that we receive. The middle circle is the processing section. We explain in simple English what’s going on in the background. For this example, we simply write a sentence explaining how the change is calculated, which is deducting the price of the item from the cash amount. Of course, depending on the problem description, it’s essential we output the change. You may or may not need to output the cash and price again, but I’ve done that also for the example. Written by Aaron Brown La Trobe University (2013) Step 2: Specify a high level solution You cannot now just develop a solution that has complex features with it. We use a defining diagram to do rigorous planning to ensure that when it comes time to programming the program, we are fully prepared. A defining diagram simply lists the Inputs, Processes and Outputs in a table- like format. In some way this is translating the diagram above, into a more complex and systematic approach. Figure 2.1: A sample defining diagram of the ‘shop’ example. INPUTS PROCESSES OUTPUTS price Change = cash - price price cash cash change  Inputs: Are the things that we know we have to enter to calculate the change. Without one or both of these, we cannot calculate. The inputs (price and cash) seen above are called variables. Variables need to have a unique but justified name which is relevant.  Processes: Is the ‘back end’ processing that is required to calculate the desired output (which is to display the change). So therefore, we write the calculation to do this, which is “Change = cash – price”.  Outputs: Are the ‘final products’ for the user to see at the end. If you have done an IPO chart before, this is somewhat similar with a few modifications to it. Step 3: Outline the Solution If there is additional information which needs to be added, this section is where you add it. If you have functions, if/else statements or anything that has not been justified, justify it in this section. Pretend that there is someone that has never seen or used your program before, and needs to know details about it. This is where you provide these details (if applicable). Step 4: Develop the outline into algorithm To do this step, we use what’s called Pseudocode and a Data Dictionary. Pseudocode is a series of logical steps that is performed for the program to be executed successfully. Written by Aaron Brown La Trobe University (2013) Figure 4.1: A sample Pseudocode with explanations for the ‘shop’ example. Always start with the ‘idea’ or ‘goal’ calculateChange() as the ‘function’. It has a name then () after it. 1. START 2. INPUT price The Pseudocode always starts with the word ‘START’ in capitals. Each line of 3. INPUT cash the Pseudocode must be numbered. 4. change = cash – price 5. DISPLAY change We must think about how the 6. STOP program will run. First, we would need to ask for the item cost and the price. We start each on a new After the inputs have been given, line, with capital INPUT, a space, we now need to calculate. This is then the variable name which we the processing stage where we now have specified in the Defining need to calculate for the output. Diagram (Step 2 (click)). After all processing and inputs have been collected, we now DISPLAY the output of ‘change’. To display or output the result, After everything has been done, to indicate that the Pseudocode has finished, we type in we type in capitals DISPLAY then capitals, STOP. This indicates the end of the the variable (which we’ve given Pseudocode. as ‘change’).
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