In this article, we will show you, how to write a C Program to Find sum of digits of a number using For Loop, While Loop, Functions and Recursion

## C Program to Find Sum of Digits of a Number using While Loop

This sum of digits in C program allows the user to enter any positive integer and then it will divide the given number into individual digits and adding those individuals (Sum) digits using While Loop

/* C Program to Find Sum of Digits of a Number using While Loop */ #include <stdio.h> int main() { int Number, Reminder, Sum=0; printf("\n Please Enter any number\n"); scanf("%d", &Number); while(Number > 0) { Reminder = Number % 10; Sum = Sum+ Reminder; Number = Number / 10; } printf("\n Sum of the digits of Given Number = %d", Sum); return 0; }

**OUTPUT**

**ANALYSIS**

This program for sum of digits in c allows you to enter any positive integer and then, that number is assigned to variable Number.

Next, Condition in the While loop will make sure that the given number is greater than 0 (Means Positive integer and greater than 0)

For the C Program to Find Sum of Digits demonstration, User Entered value: Number = 4567 and Sum = 0

**First Iteration**

Reminder = Number %10

Reminder = 4567 % 10 = 7

Sum = Sum+ Reminder

Sum = 0 + 7 => 7

Number = Number / 10

Number = 4567 / 10 => 456

**Second Iteration**

From the first Iteration, the values of both Number and Sum has been changed as Number = 456 and Sum = 7

Reminder = Number %10

Reminder = 456 % 10 = 6

Sum = Sum+ Reminder

Sum = 7 + 6 => 13

Number = Number / 10

Number = 456 / 10 => 45

**Third Iteration**

From the Second Iteration of sum of digits in c program, the values of both Number and Sum has been changed as Number = 45 and Sum = 13

Reminder = Number %10

Reminder = 45 % 10 = 5

Sum = Sum+ Reminder => 13 + 5

Sum = 18

Number = Number / 10 => 45 / 10

Number = 4

**Fourth Iteration**

From the Third Iteration, the values of both Number and Sum has been changed as Number = 4 and Sum = 18

Reminder = Number %10

Reminder = 4 % 10 = 4

Sum = Sum+ Reminder => 18 + 4

Sum = 22

Number = Number / 10 => 4 / 10

Number = 0

**Here **Number = 0 so, the while loop condition will fail

Last printf statement will print the Sum variable as output. So, the output of given variable 4567 is:

## C Program to Find Sum of Digits of a Number using For Loop

This program for sum of digits in c allows the user to enter any positive integer and then it will divide the given number into individual digits. By adding those individual digits, this c program find sum of digits of a number using For Loop

/* C Program to Find Sum of Digits of a Number using For Loop */ #include <stdio.h> int main() { int Number, Reminder, Sum; printf("\nPlease Enter any number\n"); scanf("%d", &Number); for (Sum=0; Number > 0;Number=Number/10) { Reminder = Number % 10; Sum=Sum+ Reminder; } printf("\n Sum of the digits of Given Number = %d", Sum); return 0; }

We just replaced the While loop in the above sum of digits in c example with the For loop. If you don’t understand the for loop then please refer For Loop article here: For Loop in C Programming

**OUTPUT:**

## C Program to Find Sum of Digits of a Number Using Functions

This C sum of digits in a number program allows to enter any positive integer and then it will divide the given number into individual digits and adding those individuals (C Sum of digits) using Functions

/* C Program to Find Sum of Digits of a Number Using Functions */ #include <stdio.h> int Sum_Of_Digits (int); int main() { int Number, Sum = 0; printf("\n Please Enter any number\n"); scanf("%d", &Number); Sum = Sum_Of_Digits (Number); printf("\n Sum of the digits of Given Number = %d", Sum); return 0; } int Sum_Of_Digits (int Number) { int Reminder, Sum; for (Sum=0; Number > 0;Number=Number/10) { Reminder = Number % 10; Sum=Sum+ Reminder; } return Sum; }

**OUTPUT:**

**ANALYSIS:**

In this c program to find sum of digits in a number, when the compiler reaches to Sum_Of_Digits (Number) line in main() program then the compiler will immediately jump to below function:

int Sum_Of_Digits (int Number)

We already explained LOGIC above example. Please refer C Program to Find Sum of Digits of a Given Number using While Loop Analysis section.

The last line ends with return Sum statement.

**NOTE: **If we create a function with Void then there is no need to return any value but, if we declared a function with any data type (int, float etc) then we have return something out from the function.

## C Program to Find Sum of Digits of a Number using Recursion

This program for sum of digits in c allows the user to enter any positive integer and then it will divide the given number into individual digits and adding those individuals (Sum) digits by calling the function recursively. Please refer Recursion in C for further reference

/* C Program to Find Sum of Digits of a Number using Recursion */ #include <stdio.h> int Sum_Of_Digits (int); int main() { int Number, Sum = 0; printf("\nPlease Enter any number\n"); scanf("%d", &Number); Sum = Sum_Of_Digits (Number); printf("\nSum of the digits of Given Number = %d", Sum); return 0; } int Sum_Of_Digits (int Number) { static int Reminder, Sum=0; if(Number > 0) { Reminder = Number % 10; Sum=Sum+ Reminder; Sum_Of_Digits (Number / 10); return Sum; } else return 0; }

**OUTPUT**

**ANALYSIS**

In this sum of digits in c example, When the compiler reaches to Sum_Of_Digits (Number) line in main() program then the compiler will immediately jump to below function:

int Sum_Of_Digits (int Number)

In this function, the Static variable will initialize the value only when the function called the first time.

Sum_Of_Digits (Number / 10) statement will help to call the function Recursively with the updated value. If you miss this statement in this C Program to Find Sum of Digits then, after completing the first line it will terminate.

For example, Number = 4567 then the output will be 7

Let’s see the If condition,

if (Number > 0) will check whether the number is greater than 0 or not. For Recursive functions it is very important to place a condition before using the function recursively otherwise, we will end up in infinite execution (Same like Infinite Loop).

Please be careful :)

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