To find the sum of N integers, we have to write a c program which using a for loop from 1 to N. In this C program we get the value of N from the scan f statement.

Now we write a for loop to find the sum of N numbers starting from 1. Initialize sum = 0 in the beginning. total Sum is added to the variable 'sum' in each iteration of the for loop, then the output is displayed at the end of the for loop.

#include <stdio.h> #include <conio.h> void main() { int i, N, sum = 0; clrscr(); printf("Enter an integer number\n"); /* prints enter the number and gets the value from user */ scanf ("%d", &N); for (i=1; i <= N; i++) /* beginning of for loop */ { sum = sum + i; } printf ("Sum of first %d natural numbers = %d\n", N, sum); /* prints the sum of the numbers */ }

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**OUTPUT of C program sum of n natural numbers**

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RUN1

Enter an integer number

10

Sum of first 10 natural numbers = 55

RUN2

Enter an integer number

50

Sum of first 50 natural numbers = 1275

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RUN1

Enter an integer number

10

Sum of first 10 natural numbers = 55

RUN2

Enter an integer number

50

Sum of first 50 natural numbers = 1275