C program to print all the natural numbers from 1 to N can be written in both iterative and recursive methods. In the iterative method, the task can be performed by using for loop, while loop and do-while loop.

Here, all the C programs using different loops have been covered to print the natural numbers. The algorithm, time complexity and pseudocode of the program have also been added.

#### Page content(s):

1. Algorithm

2. Pseudocode

3. Time Complexity

4. Program & Output

1. Flowchart

## 1. Algorithm to Print First N Natural Numbers

1. Take a natural number n as input.

2. Set another variable i=1

3. Iterate i from 1 to n

4. Print value of i in each iteration

## 2. Pseudocode to Print First N Natural Numbers

Input : A natural number $n$

Output : All the natural numbers from 1 to $n$

1. Procedure printUptoN($n$):

2. $i\leftarrow1$

3. Repeat

4. Print $i$

5. $i \leftarrow i+1$

6. Until $i \leq n$

7. End Procedure

## 3. Time complexity to Print First N Natural Numbers

Time Complexity: O(n)

Here, $n$ is the no. of natural numbers.

## 4. C Program & output to Print First N Natural Numbers

Code has been copied
/******************************************************************
alphabetacoder.com
C program to print all natual numbers from 1 to n  using for loop
*******************************************************************/

#include <stdio.h>

int main() {
int n, i;
//take input of the number upto which
// natural numbers will be printed
printf("Enter the upper limit = ");
scanf("%d", & n);

// iterate from 1 to n and print the number
printf("First %d natural numbers are : ", n);
for (i = 1; i <= n; i++)
printf("%d ", i);
return 0;
}


Output

#### Case 1:

Enter the upper limit = 10

First 10 natural numbers are : 1 2 3 4 5 6 7 8 9 10

#### Case 2:

Enter the upper limit = 5

First 5 natural numbers are : 1 2 3 4 5

/**************************************************
alphabetacoder.com
C program to print all natual numbers from 1 to
n using while loop
**************************************************/

#include <stdio.h>

int main() {
int n, i;
//take input of the number upto which
// natural numbers will be printed
printf("Enter the upper limit = ");
scanf("%d", & n);

// iterate from 1 to n and print the number
printf("First %d natural numbers are : ", n);
i = 1;
while (i <= n) {
printf("%d ", i);
i++;
}
return 0;
}


Output

#### Case 1:

Enter the upper limit = 10

First 10 natural numbers are : 1 2 3 4 5 6 7 8 9 10

#### Case 2:

Enter the upper limit = 5

First 5 natural numbers are : 1 2 3 4 5

/**************************************************
alphabetacoder.com
C program to print all natual numbers from 1 to
n using do-while loop
**************************************************/

#include <stdio.h>

int main() {
int n, i;
//take input of the number upto which
// natural numbers will be printed
printf("Enter the upper limit = ");
scanf("%d", & n);

// iterate from 1 to n and print the number
printf("First %d natural numbers are : ", n);
i = 1;
do {
printf("%d ", i);
i++;
} while (i <= n);

return 0;
}


Output

#### Case 1:

Enter the upper limit = 10

First 10 natural numbers are : 1 2 3 4 5 6 7 8 9 10

#### Case 2:

Enter the upper limit = 5

First 5 natural numbers are : 1 2 3 4 5