C Programming
- Print integer
- Add & subtract
- Odd & even
- Multiply & divide
- Check vowels
- Letter grade program
- Leap year program
- Sum of digits
- Prime numbers
- Sum of numbers
- Find factorial
- Fibonacci series
- Fibonacci triangle
- Number triangle
- Alphabet triangle
- Armstrong numbers
- Palindrome numbers
- Swap number
- Reverse number
- Decimal to binary
- Assembly code in C
- Matrix multiplication
- HCF & LCM
- nCr & nPr
- Print pattern
- Floyd’s triangle
- Pascal triangle
- Count digits
- Strong numbers
- Perfect numbers
- Sum of natural number
- Binary to decimal
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- Octal to decimal
- Binary to octal
- Octal to binary
- Add using pointer
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- Reverse Array
- Variable size & limit
- ASCII value of character
- Sum of array elements
- Number of element in array
- Merge two array
- Insert element in array
- Delete element from array
- Add two matrix
- Transpose matrix
- Print string
- Reverse string
- Delete vowels
- Sort string
- Remove spaces
- Swap string
- Random numbers
- Print date & time
- Print IP address
- Shut down computer
Sum of first N natural numbers in C
In this guide we will see some C program to find the sum of natural numbers. We know that natural numbers are all the positive numbers starting from 1 to any positive number.
Natural numbers : 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 ……..
To determine the sum of first N natural numbers in C, we can write the program in many ways. For example, we can make the program using any loop, mathematical formulae, function or recursion. Here we will see all the program to find the sum of first N natural numbers.
Sum of natural numbers using mathematical formulae
The mathematical formulae for determining the sum of first N natural numbers is given bellow;
Sum = n * (n + 1) / 2
We can use this formulae to calculate the sum of first N natural numbers. Let’s see the program here.
// Sum of N natural numbers using mathematical formulae
#include <stdio.h>
int main(){
int N, sum;
printf("Enter the value of N here : ");
scanf("%d", &N);
sum = (N * (N + 1)) / 2;
printf("\nSum of first %d natural numbers is = %d\n", N, sum);
return 0;
}
Output of this sum of natural number program :

Sum of natural numbers using loop in C
We can also make the sum of natural numbers program using any loop although we will use for loop to write the program. You can use any loop to determine the sum. Let’s go ahead with code.
// Sum of natural numbers using for loop
#include <stdio.h>
int main(){
int N, c, sum = 0;
printf("Enter how many numbers you want to add : ");
scanf("%d", &N);
for(c = 0; c <= N; c++){
sum = sum + c;
}
printf("\nSum of first %d natural numbers is = %d\n", N, sum);
return 0;
}
Output of program :
Enter how many numbers you want to add : 30
Sum of first 30 natural numbers is = 465
Sum of N natural numbers using array
In this C program we will use array to determine the sum.
// Sum of natural numbers using array in C
#include <stdio.h>
int main(){
int N, c, sum = 0;
printf("Enter how many number you want to add : ");
scanf("%d", &N);
int arr[N];
for(c = 0; c < N; c++){
arr[c] = c + 1;
}
for(c = 0; c < N; c++){
sum += arr[c];
}
printf("\nSum is = %d\n", sum);
return 0;
}
You will see the following output when you compile and run the program.
Enter how many number you want to add : 300
Sum is = 45150
Sum of natural numbers using function in C
// Sum of natural numbers using function in C
#include <stdio.h>
#include <conio.h>
int sum_of_num(int number);
int main(){
int n, result;
printf("Enter how many number you want to add : ");
scanf("%d", &n);
result = sum_of_num(n);
printf("\nSum is = %d\n", result);
return 0;
}
int sum_of_num(int number){
int k, sum = 0;
for (k = 0; k <= number; k++){
sum += k;
}
return sum;
}
Output :
Enter how many number you want to add : 100
Sum is = 5050
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