Unit 1 Intro to Computer Programming & Java (1/9 & 1/14)

• Data → input → Process → output → Information

• Process ←→ Storage

• Memory unit

  • RAM - Random Access Unit

  • Volatile

  • Holds both data and program instructions.

  • Shared by all programs running.

  • Ordered sequence of storage cells (bytes). Each capable of holding a piece of information.

  • Each cell has its own unique address.

  • Capacity measured in bytes, kilobytes, megabytes, gigabytes, etc…

• Decimal system

  • Base 10

  • 0 - 9

• Binary system

  • Base 2

  • 0 and 1

• Byte

• Kilobyte → 1,024 (2^10)

• Megabyte → about a million bytes (2²^0)

• Gigabyte → about a billion bytes (2³^0)

• Tbyte → about a trillion bytes (2^40)

• Pbyte → (2^50)

• Central processing unit (CPU)

  • Executes program instructions

  • Components

    • Control unit: controls the order in which the program instructions are executed.

    • Arithmetic/logic unit (ALU): performs arithmetic operations and makes logical decisions.

    • Speed measured in hertz, kilohertz, megahertz, etc…

  • Fetch - Execute - Decode cycle

    • Fetch

      • Fetch the instructions located in RAM

      • Copy the instruction to the instruction register

    • Decode

      • Input data

      • Perform an arithmetic/logical operation

      • Output data

    • ALU

      • Get data, if needed, from Memory to CPU registers

    • Execute instructions

• System Software

  • Operating system

    • Administers all the computer resources and presents itself as the interface between the user and the computer.

      • Starts working when the computer is turned on.

      • Enables the user to access programs, manage files, and complete other tasks.

• Application Software

  • Programs that enable the user to accomplish specific kinds of tasks.

    • Example

      • Word processing

      • Spreadsheets

      • Database management systems

• Programming Life-cycle Phases

  • Problem-solving

  • Impemation

  • Maintenance

• IPO - Input/Processing/Output

  • Input

    • Assigning values

    • Keyboard

    • File(s)

  • Processing

    • Calculations

  • Output

    • Screen

    • File(s)

• Comments in Java

  • /*…. */

  • //

• Class

  • If something is capitalized, it’s because it’s from a class and it MUST be capitalized.

• Output

  • System.out.println("Hello World!!");

/*
 * Hayley Pappas
 * 
 * Hello.java
 * 
 * Display the message "Hello World!!"
 */

public class Hello {
	public static void main(String[] args)
	{
		// Display the message "Hello World!!"
		System.out.println("Hello World!!");
	}
}

• Declaration

  • DataType Variable1, ……. ;

/*
 * Hayley Pappas
 * 
 * Rectangle.java
 * 
 * Given the width (1234.5) and the height (10.0) of a rectangle, 
 * calculate its area, and display the results.
 */

public class Rectangle {
	public static void main(String[] args)
	{
		// Variables
		double width, height, area;
		
		// Intro
		System.out.println("Rectanlge Area Calculator ...");
		System.out.println();  // Blank line
		
		// Assign values to the width & height
		width = 1234.5;
		height = 10.0;
		
		// Calculate area
		area = width * height;
		
		// Display result
		System.out.println("The area of a " + width + " by " + height 
				+ " rectangle is " + area + ".");
	}

}