1. Using Iterative Approach

#include <stdio.h>

int main(){

int num;

//this variable will be used to save the result of the sum

int sum = 0;

printf("Enter any positive number....");

scanf("%d",&num);

for(int i=1;i<=num;i++){

sum = sum + i;

}

printf("The sum of the numbers from 1 to %d is %d",num,sum);

return 0;

}

2. Using a Function

#include <stdio.h>

//this function will take a number as argument and

//retrun the sum upto that number to the calling function

int getSum(int num){

//this variable will be used to save the result of the sum

int sum = 0;

printf("The sum of the numbers from 1 to %d is\n",num);

for(int i=1;i<=num;i++){

sum = sum + i;

printf("%d+",i);

}

return sum;

}

int main(){

int num;

printf("Enter Any number ::");

scanf("%d",&num);

//number is passed as argument to the fun

int sum = getSum(num);

printf("=%d",sum);

return 0;

}

3. Using Function Recursion

#include <stdio.h>

//this function will take a number as argument and

//call itself till the number > 0

int getSum(int num){

//base condition

if(num>0){

num>1?printf("%d+",num):printf("%d",num);

return num + getSum(num-1);

}

}

int main(){

int num;

printf("Enter Any number ::");

scanf("%d",&num);

printf("The sum of the numbers from 1 to %d is\n",num);

//number is passed as argument to the fun

int sum = getSum(num);

printf("=%d",sum);

return 0;

}