For a better understanding, we always recommend you to learn the basic topics of C programming listed below:

In this C program, we have to find out the sum of all integers of the given number. If the number is 250, we have to add the digits of the number** **(2+5+0) and have the output as** **7.

Here what we are doing is, Add the header files into the program to use the built-in input and output functions. After that, accept an integer from the user and save that integer as long int in a variable called '**num**'.

Now Copy that integer to a temporary variable **temp **for keeping the copy of the original number. Open a `while loop`

until the number is greater than Zero. Inside that while loop, we extract each digit from the number using the **Mod **operator and add it to the **Sum**. Then divide the number by 10 to remove the last digit.

Finally, we display the value of the **Sum **variable as a result of using a long integer.

```
while (testExpression)
{
// codes inside the body of a while
}
```

Here `while loop`

evaluates the test expression, if the test expression is True, We execute the code inside the `while loop`

. This process continues until the test expression is False.

**STEP 1:** Include the header files to use the built-in functions in the C program.

**STEP 2:** Declare the variable** num, temp, digit, sum** as `long integer`

, and set **sum=0**.

**STEP 3: **Read the number from the user and save it into the variable **num**.

**STEP 4:** Assign **temp=num**.

**STEP 5:** By using a `while loop`

with the condition **num>0**, calculate **digit=num**, **sum=sum+digit**, **num=num/10**.

**STEP 6:** Display the given number as '**temp**'.

**STEP 7:** Display Sum of digits as a **sum**.

` ````
#include <stdio.h>
void main() {
int num, temp, digit, sum = 0; /* declares the variables for the program */
printf("Enter the number\n");
scanf("%d",& num); /* accepting and storing the number in a variable */
temp = num;
while (num > 0) /* initialize the while loop */ {
digit = num%10; /* number is mod by 10 to get reminder and sum is added */
sum = sum + digit;
num =num/ 10;
}
printf("Given number =%d \n", temp);
printf("Sum of the digits %d =%d \n", temp, sum);
} /* End of main()*/
```

Enter the number 123456 Given number =123456 Sum of the digits 123456 =21