1. First, define three integer variables to store positive integers, temporary variables and the sum of each digit.

2. Assign a value to the variable sum, with the initial value being 0.

3. Next, enter a positive integer and save it in variable n.

4. Assign a value to the temporary variable so that its value is equal to the value of a positive integer.

5. Use the while statement to judge. The judgment condition is that n is not equal to 0.

6. When the conditions are met, find the sum of the digits of the positive integer.

7. Remove the number of digits that have been summed from the positive integer.

8. Finally, output the sum of the digits in the positive integer.

9. Run the program and enter any positive integer, and the computer will output the sum of its digits.