# C Program to Print Prime Numbers From 1 to 100

In this post, we will learn how to print prime numbers from 1 to 100 using the C Programming language.

In the previous post, you have seen how to check whether a number is prime or not. Today, we will print all the prime numbers lying between 1 to 100 using the following approaches:

1. Using For Loop
2. Using While Loop

So, without further ado, let’s begin this tutorial.

## C Program to Print Prime Numbers From 1 to 100

```// C Program to Print Prime Numbers From 1 to 100
#include <stdio.h>
int main(){
int i, num, count;

// Checking for prime numbers
for (num = 1; num <= 100; num++){
count = 0;
for (i = 2; i <= num/2; i++){
if (num % i == 0){
count++;
break;
}
}

// Checking and Printing Prime Numbers
if (count == 0 && num != 1){
printf("%d \n", num);
}
}
return 0;
}
```

Output

``````2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97
``````

## How Does This Program Work ?

```    int i, num, count;
```

In this program, we have declared three integer data type variables named i, num, and count.

```    for (num = 1; num <= 100; num++){
count = 0;
for (i = 2; i <= num/2; i++){
if (num % i == 0){
count++;
break;
}
}
```

For every number, we check its factor. If that iteration of the for loop contains a factor, then count values increases.

```        // Checking and Printing Prime Numbers
if (count == 0 && num != 1){
printf("%d \n", num);
}
```

Now, all the numbers which don’t have a factor are prime numbers. We print all those numbers using printf() function.

## C Program to Print Prime Numbers From 1 to 100 Using While Loop

```// C Program to Print Prime Numbers From 1 to 100 Using While Loop
#include <stdio.h>
int main(){
int i, num = 1, count;

// Checking for the factors
while (num <= 100){
count = 0;
i = 2;
while (i <= num/2){
if (num % i == 0){
count++;
break;
}
i++;
}

// Printing prime numbers
if (count == 0 && num != 1){
printf("%d \n", num);
}
num++;
}
return 0;
}
```

Output

``````2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97
``````

## Conclusion

I hope after going through this post, you understand how to print prime numbers from 1 to 100 using the C Programming language.

If you have any doubt regarding the program, then contact us in the comment section. We will be delighted to assist you.

### 1 thought on “C Program to Print Prime Numbers From 1 to 100”

1. // C Program to Print Prime Numbers From 1 to 100
#include
int main(){
int i, num, count;

// Checking for prime numbers
for (num = 1; num <= 100; num++){
count = 0;
for (i = 2; i <= num/2; i++){
if (num % i == 0){
count++;
break;
}
}

// Checking and Printing Prime Numbers
if (count == 0 && num != 1){
printf("%d \n", num);
}
}
return 0;
}

***I don't understand, if I put 0 at the start of count variable (ie, int i,num,count=0 like this) the code is not working. But if you put "count=0" inside the for loop it is working. Why is this happening?