Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java code implements a very basic calculator that takes two integer numbers and an operator choice from the user, then performs the corresponding arithmetic operation.

Here's a step-by-step breakdown:

1. Import Scanner: The line import java.util.Scanner; brings in the Scanner class from Java's utility library. This class is essential for reading input from the user (like numbers or text) via the console.
2. Class Definition: class prog4 defines a class named prog4. In Java, all code resides within classes.
3. Main Method: public static void main(String args[]) is the entry point of any Java application. When you run this program, execution begins here.
4. Create Scanner Object: Scanner input = new Scanner(System.in); creates an object of the Scanner class, named input. System.in indicates that the scanner should read input from the standard input stream, which is typically the keyboard.
5. Get First Number:
   • System.out.print("Enter the First Number: "); displays a prompt on the console asking the user to enter the first number. print keeps the cursor on the same line after the prompt.
   • int a = input.nextInt(); reads the integer value typed by the user and stores it in an integer variable named a.
6. Get Second Number:
   • System.out.print("Enter the Second Number: "); prompts for the second number.
   • int b = input.nextInt(); reads the second integer and stores it in variable b.
7. Get Operator Choice:
   • System.out.print("Enter Operator (1:Addition, 2:Subtraction, 3:Multiplication, 4:Division, 5:Exit): "); prompts the user to choose an operation by entering a number from 1 to 5.
   • int op = input.nextInt(); reads the user's integer choice for the operator and stores it in variable op.
8. Perform Operation (Conditional Logic):
   • The code then uses a series of if-else if statements to check the value of op:
     • if (op == 1): If op is 1, it means the user chose addition. System.out.println("a+b is "+(a+b)); calculates a + b and prints the result to the console, prefixed with "a+b is ".
     • else if (op == 2): If op is 2, it performs subtraction (a - b) and prints the result.
     • else if (op == 3): If op is 3, it performs multiplication (a * b) and prints the result.
     • else if (op == 4): If op is 4, it performs integer division (a / b) and prints the result.
   • Notice that if op is 5 (Exit) or any other number, no operation is performed, and nothing specific is printed for those cases by this if-else if structure.
9. Close Scanner: input.close(); releases the system resources associated with the Scanner object. It's good practice to close resources when they are no longer needed to prevent resource leaks.

Algorithm

1. Initialize a Scanner object to read user input from the console.
2. Prompt the user to enter the first integer number.
3. Read the first integer number and store it in a variable (e.g., a).
4. Prompt the user to enter the second integer number.
5. Read the second integer number and store it in a variable (e.g., b).
6. Prompt the user to choose an arithmetic operation by entering a specific number (1 for Addition, 2 for Subtraction, 3 for Multiplication, 4 for Division, 5 for Exit).
7. Read the user's operator choice and store it in a variable (e.g., op).
8. Based on the value of op, use conditional statements:
   • If op is 1, calculate a + b and display the result.
   • If op is 2, calculate a - b and display the result.
   • If op is 3, calculate a * b and display the result.
   • If op is 4, calculate a / b and display the result.
9. Close the Scanner object to release system resources.