An Object-Oriented Approach to Programming Logic and Design - Chapter Notes

Introduction

• This chapter provides foundational concepts in programming logic and design.

• Topics covered include:

  • Literals, variables, and named constants

  • Value assignment to variables

  • Definition and naming of identifiers

  • Arithmetic operations

  • Attributes of good program design

  • Introduction to programming structure

Creating an Application Class

• Application: A software system designed for data collection, processing, and presentation to aid decision-making.

• Examples of applications include:

  • Sales dashboard

  • Hospital reporting system

  • Student grading system

  • Inventory management system

  • National disease monitoring dashboard

Using Literals, Variables, and Named Constants

• Programs accept input in various forms:

  • User input through interactive programs

  • Data from storage devices in batch processing

• Data Types:

  • Literals (unnamed constants)

  • Variables

  • Named constants

Understanding Unnamed, Literal Constants and Their Data Types

• Types of literals:

  • Numeric literals: Numbers without quotation marks.

  • Example: 613 (cannot contain alphabetic characters).

  • String literals: Text enclosed in quotation marks.

  • Example: "Jenna" (can include digits, punctuation).

Understanding Variables

• Variables:

  • Named memory locations that can hold varying values.

  • Only store one value at any time.

• Pseudocode example of variable use:

  • Doubling input number:
    INPUT number double = number * 2 OUTPUT double

Working with Variables

• Declaration Requirements:

  • Must declare variables before use.

  • A variable declaration includes the data type and identifier:

  • Example data types in the text:

    • num for numeric data

    • string for string data

• Sample Variable Declarations:

  • num mySalary

  • string myName

Understanding a Variable’s Data Type

• Each variable has a data type:

  • Numeric variable: Holds digits, used in mathematical operations.

  • Example: testScore = 96.

  • String variable: Holds text, including digits but not used in arithmetic operations.

  • Example: zipcode = "08202".

• Assignment Validity:

  • Correct type assignment only:

  • Valid: num taxRate = 2.5

  • Invalid: num taxRate = "2.5"

Working with Variables (cont’d)

• Initializing Variables:

  • Providing initial values to variables:

  • Valid examples:

    • num yourSalary = 14.55

    • string yourName = "Pat"

• Garbage Values:

  • Uninitialized variables contain unknown values known as garbage, which are usually illegal for output.

Naming Variables

• Importance of meaningful names for variables.

• Names are associated with specific memory addresses.

Assigning Values to Variables

• Assignment statement example:

  • myAnswer = myNumber * 2 (performs a calculation and stores the result).

• Assignment operator: =

  • A binary operator that operates from the right to left.

  • The right side is evaluated before assignment; the left side must be a memory address.

Declaring Named Constants

• Similar to variables but assigned a value only once.

• Used to identify immutable values during execution.

• Improves program clarity and maintainability.

• Naming convention: ALL CAPITALS with underscores (e.g., SALES_TAX).

Identifier Naming

• Identifier: Name of programming objects (class, method, variable).

• Common rules:

  • Can include letters and digits.

  • Special characters allowed in some languages (e.g., _).

  • Cannot start with a digit.

  • No white space allowed.

  • Cannot be keywords.

  • Case sensitivity applies.

Choosing Identifiers

• General guidelines for naming identifiers:

  • Use nouns or nouns combined with adjectives.

  • Ensure names are meaningful (self-documenting).

  • Keep names pronounceable.

  • Minimize abbreviations.

Performing Arithmetic Operations

• Standard arithmetic operators:

  • + (addition)

  • - (subtraction)

  • * (multiplication)

  • / (division)

• Valid assignment statements:

  • someNumber = 2 * 25 / 5

  • someNumber = anotherNumber + 3

  • totalScore = 0

  • totalScore += 10 (increment totalScore).

• Invalid statements:

  • 3 + 5 = someNumber (left side not a memory location).

Rules of Operator Precedence

• Evaluates parentheses first.

• Multiplication and division from left to right.

• Addition and subtraction from left to right.

Writing Clear Prompts and Echoing Input

• Prompts: Messages that request user input, should be clear.

• Echoing input: Repeating user input to aid with error identification.

Designing Clear Statements

• Example demonstrating prompts and echoes effectively.

Features of Good Program Design

• Best practices for maintainable programs include:

  • Using comments where necessary.

  • Choosing meaningful identifiers.

  • Designing clear statements.

  • Writing clear prompts and echoing input.

  • Maintaining good programming habits.

• Internal documentation: Comments within code for clarity.

• External documentation: Documentation outside the program.

An Introduction to Structure

• Structures represent basic units of programming logic:

  • Sequence Structure: Executes actions linearly with no decision-making (e.g., driving directions).

  • Selection Structure: Chooses a path based on conditions.

  • Loop Structure: Repeats instructions based on a condition.

Summary

• Data values can be stored as literals, variables, and named constants (numeric or string).

• Naming identifiers follow specific rules.

• Variables are named memory locations allowing changing content.

• Data types dictate what values a variable can hold.

• Declaration statements specify variable types and identifiers.

• Named constants are assigned values once.

• Know the four standard arithmetic operations and their precedence.

• Practice good programming habits, including comments, meaningful identifiers, and clear statements.

• Understand programming structures: sequence, selection, and loop.

Exercise

• Write pseudocode that:

  • Prompts the user for their name and score.

  • Echoes the input received.

  • Uses a selection structure to return "Pass" or "Fail" based on score.

  • Concludes with a "Thank you" message.