Expt 1 - Part 1, Part 2 & Part 3

Explanation

This Java code is designed to calculate the sum of the digits of an integer provided by the user. For instance, if the user enters 123, the program will calculate 1 + 2 + 3 and output 6.

The program begins by setting up a way to receive input from the user using the Scanner class. It prompts the user to "Enter a number:", reads that number, and stores it in an integer variable called num. Another integer variable, sum, is initialized to 0; this variable will accumulate the sum of the digits.

The core logic resides within a while loop. This loop continues to execute as long as the value of num is not zero. Inside the loop, two key operations occur:

1. sum += num % 10;: The modulo operator (%) gives the remainder of a division. When num is divided by 10, the remainder is always its last digit (e.g., 123 % 10 is 3). This last digit is then added to the sum variable.
2. num = num / 10;: Integer division (/) discards any fractional part. When num is divided by 10 using integer division, its last digit is effectively removed (e.g., 123 / 10 becomes 12).

These two steps repeatedly extract the last digit, add it to the sum, and then remove it from the original number, until num eventually becomes 0. Once num is 0, it means all digits have been processed. The loop terminates, and the program prints the final calculated sum of digits to the console. Finally, it closes the Scanner object to release system resources.

Algorithm

The algorithm to find the sum of digits of a number can be described as follows:

1. Start the program.
2. Initialize a Scanner object to read input from the console.
3. Prompt the user to enter an integer.
4. Read the integer entered by the user and store it in a variable, let's call it num.
5. Initialize another variable, sum, to 0. This variable will store the accumulated sum of digits.
6. Begin a loop that continues as long as num is not equal to 0. a. Extract the last digit: Calculate the remainder when num is divided by 10 (num % 10). This gives the rightmost digit. b. Add to sum: Add the extracted last digit to the sum variable. c. Remove the last digit: Update num by performing integer division of num by 10 (num = num / 10). This effectively removes the rightmost digit.
7. Exit the loop when num becomes 0 (indicating all digits have been processed).
8. Print the final value of sum to the console.
9. Close the Scanner object to release resources.
10. End the program.