Raptor programming

Chapter 3 Developing a Program AITT 4300 DIGITAL COMPUTER STRUCTURES

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

3.1 The Program Development Cycle Problem solving principles ◦ Completely understand the problem

◦Devise a plan to solve it ◦ Carry out the plan ◦ Review the results

Writing a program 1) Analyze the problem 2) Design the program 3) Code the program 4) Test the program

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

1. Analyze the problem Identify desired results (output)

Determine input needed to produce those results

Example: Create a program to generate 6 numbers to play the lottery ◦ Is 7, 7, 7, 7, 7, 7 ok? ◦ Is ‐3, 0, 8, 9, 689, 689 ok? ◦ Is 1, 2, 6, 47.98765, 88, 93.45 ok? ◦ These are all 6 numbers but we see we must be more specific ◦ Desired results: 6 different positive integers within the range of 1 to 40

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

2. Design the program

Create a detailed description of program ◦ Use charts, models, or ordinary language (pseudocode)

Identify algorithms needed ◦ Algorithm: a step‐by‐step method to solve a problem or complete a task

Algorithms must be: ◦ Well defined ◦ Well ordered ◦ Must produce some result ◦ Must terminate in a finite time

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

3. Code the program

Translate charts, models, pseudocode, or ordinary language into program code

Add statements to document what the code does ◦ Internal documenation ◦ External documentation

Each programming language uses its specific syntax

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

Syntax

Correct syntax for telling your friend where you put a cheese sandwich is: “I have put it on the table.”

Incorrect use of English syntax to say: “I have it on the table put.”

All the right words are there, but without proper syntax, the sentence is gibberish in English. But translated word for word, the second sentence is correct syntax in German.

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

4. Test the program

In analysis phase: continually ask questions ◦ Did I interpret data correctly? ◦ Does program fulfill requirements? ◦ Are my formulas or procedures correct? Etc…

In design phase: use desk‐checking to walk through the program

In coding phase: software will alert you to errors in syntax but not in the logic of the program

Finally, test your program with as many sets of test data as possible ◦ Use good data, bad data, data you know the answers for, etc.

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

Additional Steps in the Cycle

o Create an outline of the program so that it is apparent what major tasks and subtasks have to be accomplished and the relationships among these tasks

o Describe in detail how each of these tasks is to be carried out

To put a commercial program (produced by a software publishing company) you may need to: ◦ Create a user’s guide ◦ to help users can understand the intricacies of the program

◦ Create help files ◦ installed with the software for users to get on‐screen help

◦ Train employees to provide telephone or web‐based customer support ◦ Duplicate disks and accompanying materials for distribution ◦ Advertise the program to attract buyers

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

Program development is a process

 Program development is a cyclical process that often requires returning to earlier steps and, with complex programs, may take many months

The design process may uncover flaws in the analysis

Coding may find problems leading to modifications or additions to the design

Testing inevitably uncovers problems that require returning to previous phases

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

The Sale Price Example A local department store wants to develop a program which, when given an item’s original price and the percentage it is discounted, will compute the sale price, with sales tax.

Output required: name of item, discounted price, amount of sales tax, total price

Variables needed: ItemName, SalePrice, Tax, TotalPrice

Input required: name of item, original price, percent discounted

More variables: OriginalPrice, DiscountRate

Formulas required:

New variable needed: AmountSaved

SalePrice = OriginalPrice – AmountSaved

AmountSaved = OriginalPrice * (DiscountRate/100)

Tax = SalePrice * .065

TotalPrice = SalePrice + Tax

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

Design: Input  Processing  Output Input Perform Calculations (Process) Output

Input variables: Computations: Display:

ItemName AmountSaved = OriginalPrice * DiscountRate/100 TotalPrice

DiscountRate SalePrice = OriginalPrice – AmountSaved ItemName

OriginalPrice Tax = SalePrice * .065 Tax

TotalPrice = SalePrice + Tax SalePrice

3.2 Program Design Modular Programming

To begin designing a program: identify the major tasks the program must accomplish.

Each of these tasks becomes a program module. ◦ if needed, break each of these fundamental “high‐level” tasks into submodules

◦ Some submodules might be divided into submodules of their own ◦ this process can be continued as long as necessary ◦ Identifying the tasks and subtasks is called modular programming

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

Using Modules and Submodules  A module performs a single task.

 A module is self‐contained and independent of other modules.

 A module is relatively short. Ideally, statements should not exceed one page.

Benefits of Modular Programming o program is easier to read

o easier to design, code, and test the program one module at a time

o different program modules can be designed and/or coded by different programmers

o a single module may be used in more than one place in the program

o modules that perform common programming tasks can be used in more than one program

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

Pseudocode: uses short, English‐like phrases to describe the outline of a program

Example: pseudocode for the Sale Price Program with modules: Input Data module

Prompt for ItemName, OriginalPrice, DiscountRate Input ItemName, OriginalPrice, DiscountRate

Perform Calculations module Set AmountSaved = OriginalPrice * (DiscountRate/100) Set SalePrice = OriginalPrice – AmountSaved Set Tax = SalePrice * .065 Set TotalPrice = SalePrice + Tax

Output Results module Write ItemName Write OriginalPrice Write DiscountRate Write SalePrice Write Tax Write TotalPrice

PRELUDE TO PROGRAMMING, 6TH EDITION BY ELIZABETH DRAKE

Refined Pseudocode for the Sale Price Program Input Data module

Write “What is the item’s name?” Input ItemName Write “What is its price and the percentage discounted?” Input OriginalPrice Input DiscountRate

Perform Calculations module Set AmountSaved = OriginalPrice * (DiscountRate/100) Set SalePrice = OriginalPrice – AmountSaved Set Tax = SalePrice * .065 Set TotalPrice = SalePrice + Tax

Output Results module Write “The item is: “ + ItemName Write “Pre-sale price was: “ + OriginalPrice Write “Percentage discounted was: “ + DiscountRate + “%” Write “Sale price: “ + SalePrice Write “Sales tax: “ + Tax Write “Total: $” + TotalPrice