Programming Logic and Design: Input, Processing, and Output

Program Design

• First step: Design (using flowcharts and pseudocode).

• Steps: Understand tasks, determine steps (create algorithm).

• Program Development Cycle: Design -> Code -> Clear syntax errors -> Create executable -> Check for logic errors -> Debug.

• Pseudocode: "Fake code" model, no syntax rules; easily translated to actual code.

• Flowcharts: Graphical depiction of program steps.

  • Connector Symbol: Breaks flowcharts into smaller, side-by-side ones.

  • Off-Page Connector Symbol: Links flowcharts across different pages.

Output, Input, and Variables (IPO)

• Output: Data generated and displayed.

• Input: Data a program receives.

• Variables: Storage locations in memory.

• Typical Program Sequence: Input received -> Process performed -> Output produced.

• IPO Chart: Describes Input, Processing, Output of a program.

• Keywords: Display for output, Input for user values.

• Sequence: Lines execute in order.

• String Literals: Sequence of characters.

• Variable Naming Rules: One word (no spaces), avoid punctuation, first character usually not a number, indicative name, camelCase popular.

Variable Assignment & Calculations

• Assignment: Setting a variable's value (e.g., Set price = 20) or through user input.

• Calculations: Performed using math operators.

  • +: Addition

  • -: Subtraction

  • *: Multiplication (Asterisk)

  • /: Division (Quotient)

  • MOD: Modulus (Remainder)

  • ^: Exponent (Caret)

  • Expressions result stored in variables (e.g., Set sale = price - discount).

Variable Declarations & Data Types

• Declaration: Includes variable name and data type (Declare Real grossPay).

• Data Type: Defines data stored:

  • Integer: Whole numbers.

  • Real: Whole or decimal numbers.

  • String: Any series of characters.

• Initialization: Variables should be initialized (e.g., to $0$) to prevent logic errors.

Named Constants

• Definition: A name representing an unchangeable value.

• Benefits: Self-explanatory programs, easy value modification in one place.

• Example: Constant Real INTEREST_RATE = 0.069.

Hand Tracing a Program

• Purpose: Simple debugging process for hard-to-find errors.

• Method: Create a chart with columns for each variable and rows for each line of code.

Documenting a Program

• External Documentation: Describes program aspects for the user.

• Internal Documentation (Comments): Explains how parts of the program work for programmers.

  • Syntax: // for line comments, /* ... */ for multiline comments.

Language Focus: Java

• Program Structure: public class ClassName { public static void main(String[] args) { /* code */ } }

• Output:

  • `System.out.println(