C Program to Display Prime Numbers Between Two Intervals

Display Prime Numbers Between Two Intervals

``````
#include <stdio.h>

int main(){
int low, high, i, flag;
printf("Enter two numbers(intervals): ");
scanf("%d %d", &low, &high);
printf("Prime numbers between %d and %d are: ", low, high);

// iteration until low is not equal to high
while (low < high) {
flag = 0;

// ignore numbers less than 2
if (low <= 1) {
++low;
continue;
}

// if low is a non-prime number, flag will be 1
for (i = 2; i <= low / 2; ++i) {

if (low % i == 0) {
flag = 1;
break;
}
}

if (flag == 0)
printf("%d ", low);

// to check prime for the next number
// increase low by 1
++low;
}

return 0;
}``````

Output

```Enter two numbers(intervals): 20
50
Prime numbers between 20 and 50 are: 23 29 31 37 41 43 47
```

In this program, the `while` loop is iterated ( `high-low-1`) times.

In each iteration, whether `low` is a prime number or not is checked, and the value of `low` is incremented by `1` until `low` is equal to `high`.

Display Prime Numbers when Larger Number is Entered first

``````
#include <stdio.h>

int main(){
int low, high, i, flag, temp;
printf("Enter two numbers(intervals): ");
scanf("%d %d", &low, &high);

// swap numbers if low is greather than high
if (low > high) {
temp = low;
low = high;
high = temp;
}

printf("Prime numbers between %d and %d are: ", low, high);
while (low < high) {
flag = 0;

// ignore numbers less than 2
if (low <= 1) {
++low;
continue;
}

for (i = 2; i <= low / 2; ++i) {
if (low % i == 0) {
flag = 1;
break;
}
}
if (flag == 0)
printf("%d ", low);
++low;
}

return 0;
}``````

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Disclaimer: The information and code presented within this recipe/tutorial is only for educational and coaching purposes for beginners and developers. Anyone can practice and apply the recipe/tutorial presented here, but the reader is taking full responsibility for his/her actions. The author (content curator) of this recipe (code / program) has made every effort to ensure the accuracy of the information was correct at time of publication. The author (content curator) does not assume and hereby disclaims any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether such errors or omissions result from accident, negligence, or any other cause. The information presented here could also be found in public knowledge domains.```