C Foundation

What is C? C Compiler Installation C Extensions C Compiler C Interpreter C Program Structure

C Basics

C Keywords C Data Types C Identifiers C Variables C Constant C Escape Sequences C Constant and Volatile C Typecast


What is Operator C Comma Operator C Arithmetic Operators C Relational Operators C Logical Operators C Bitwise Operators C Conditional Operators C : : Operator C Operator Priority

Basic IO's

Basic IO's C Formatted Functions C Unformatted Functions C Common Functions

Control Statements

What is Control Statement C if Statement C if else Statement C Nested if Statement C Else if Statement C Break Statement C Continue Statement C Switch Statement C Goto Statement


What is Control Loop C for Loop C Nested for Loop C while Loop C Nested while Loop C do while Loop C Nested do while loop


What is Function C User Defined Functions C Recursion C Passing Parameters


Scope C Local Scope C Global Scope

Storage Classes

What is Storage Class C Auto C Extern C Static C Register


What is Array C One Dimensional Array C Two Dimensional Array C Multi Dimensional Array C Arrays Of Strings


What is String C String Functions


What is Pointer C Pointers Arithmetic C Pointer to Pointer C Pointers and Arrays C Pointers and Strings C Pointer to Functions Void Pointers Null Pointers C Null and Void Pointer


What is Structure C Struct within Struct C Array within Structure C Pointer to Structure C Structure and Function C Enum C Bitfield Structure C Type def


What is Union


What is File C read a file C write a file C File Handling C Error Handling C Low Level Disk I/O C Other file functions

Memory Allocation

What is Memory Allocation C Malloc() C Calloc() C Free() C Realloc() C Coreleft()

C Reference

All ASCII Code Basic C Questions

C Interview

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The ones who are crazy enough to think they can change the world are the ones who do.
- Steve Jobs

C Sum of n Digits

Here your task is to add n digits of a number for one time i.e) if user entered 786 you have to reply 18 which means 7 + 8 + 6.

C Program - To Sum n Digits

Let us write a c program to sum n digits of a number.

#include <stdio.h>
int main()
int num, r, s = 0;
printf("Enter a positive integer: ");
while(num != 0)
r = num % 10;
s = s + r;
num = num / 10;
printf("\nThe sum of the digit is : %d ", s);
return 0;
Enter a positive integer: 756
The sum of the digit is : 18


Here we slice digits from last and summation the digits simultaneously. By looking at the program r = num % 10 slicing last digit from a variable num and storing it in a variable r. s = s + r summation is done here and the result is stored in a variable s. num = num/10 removing last digit completely from num variable.

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