Please write code in C and please add comments

Questions

Write a loop based C program that takes a positive number as input from the user via the

keyboard and calculates the sum of all the individual digits in that number. Display the

result. Note that if the user enters a negative number, your program must keep asking the

user until a valid number is entered. Below are some sample outputs for how the program

should behave. Note that the input number is not necessarily $5-$digit.

Sample Run $1$:

Enter a positive nubmber: $38912$

Sum of all digits in $38912$ is $23$

Sample Run $2$:

Enter a positive nubmber: $432$

Sum of all digits in $432$ is $9$

Sample Run $3$:

Enter a positive nubmber: $-278239$

You entered an invalid number

Re$-$enter the number: $-3456$

You entered an invalid number

Re$-$enter the number: $123456$

Sum of all digits in $123456$ is $21$