**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.

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## 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.

3. **Repeat**

4. **Print** $i$

5.

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

/****************************************************************** 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

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