Cosc175 - Define Problem/Design Solution/Pseudocode/Trace 1 DEFINE THE PROBLEM.

cosc175 - Define Problem/Design Solution/Pseudocode/Trace

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DEFINE THE PROBLEM


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Analysis of the Problem

1. Determine what is given - input =>nouns, adjectives

2. Determine what is required - output =>nouns, adjectives

3. Determine the transformations needed(processing)-actions needed to produce the required

output

=>verbs, adverbs


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Inputs and Outputs

• Determine data that is input to the problem, data that will be output from the problem

• Nouns• We call the input and output data-variables• We use a particular naming convention

– No spaces– Meaningful names– Usually begin with lowercase– Examples: roomWidth, numPeople, studentName


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Example 1:

Input

Processing

Output

number1

total

number2

number3

Read three numbers, add them together and print the total.Read three numbers, add them together and print the total.Step 1 – define inputs and outputs(hint: look at nouns)Break up several values into separate variables


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Example 1:

Input

Processing

Output

number1

Read three numbers

total

number2

Add numbers together

number3

Print total number

Read three numbers, add them together and print the total.Read three numbers, add them together and print the total.Step 2: define list of actions. Hint: Use verbs,these steps usually involve the input and output defined in step 1


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Example 2:

Input

Processing

Output

maxTemp avgTemp

minTemp

Write a program to prompt the operator for the maximum and minimum temperature readings on a particular day, accept those readings as integers, and calculate and display on the screen the average temperature.


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Example 2:

Input

Processing

Output

maxTemp Prompt for temps

avgTemp

minTemp

Calculate average

Display average

Write a program to prompt the operator for the maximum and minimum temperature readings on a particular day, accept those readings as integers, and calculate and display on the screen the average temperature.


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PLAN THE SOLUTION


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Plan the Solution

• Outline the Solution– Major processing steps involved– Major subtasks– Major control structures– Major variables and record structures– Mainline logic

• Develop the outline into an algorithm• Test the algorithm for correctness


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Structured Programming

• Top Down Design & Development

• Modularity

• Control structures– sequence– selection or IF-THEN-ELSE– repetition or looping


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Design/Plan the solution

• Algorithm – a step by step procedure for solving a problem

• Programs - implementations of algorithms– Set of instructions

• flowcharts

• pseudocode– test solution for correctness - trace


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Pseudocode

• structured concise English statements used to state operations

• language independent,no standard

• use words and phrases that are in line with basic computer operations


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Pseudocode

1. Write statements in simple English2. Write each instruction on a separate

line.3. Use keywords and indentation for

control structures.4. Write instructions from top to bottom,

with only one entry and one exit.5. Groups of statements may be formed

into modules.


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Pseudocode

1. Input - receiving information• keywords - Read, Get, Input• Read - receive information from a record on a

file• Get - receive information from the keyboard.

Read studentNameGet systemDateRead num1,num2Get taxCode

• use one verb followed by one or more nouns


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Pseudocode

2. Output– putting information out

• Put, Output,Display - screen• Print - printer• Write - file

– Print smaller.– Print "Program Completed"– Write customer_record to file– Output totalTax– Display "End of Data"


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Output continued

• Labels– Display "label"

• statement inside quotes is printed as it appears

– Display "x" // if x = 5• Yields x

– Display x• yields 5

– Display "X = " and x• yields: X = 5


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Pseudocode

3.Arithmetic• use name of the operation or algebraic symbol• add,subtract,multiply, divide, exponentiation• + - * / **• x = algebraic expression

– count = count + 1– netPay = hourlyPayRate * hoursWorked– salesTax = cost * 0.10– totalPrice = price + salesTax


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Pseudocode

4. Assignment - place information into a storage location

• Initialize, Set - give variable initial value• Save,Store - save info for later• = //preferred

y = 3 note: does not mean equality– could involve calculation:– area = length * width

Cosc175 - Define Problem/Design Solution/Pseudocode/Trace 1 DEFINE THE PROBLEM.

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