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Programming for Problem Solving [ Lab Programs ]


Write a program that finds if a given number is a prime number .

Algorithm

start
	step1: Read number
	step2: for i := 2 to number/2 step 1 do
	step3: 	if number % i = 0 then 
	step4: 		count := count +1
	step5: 		break	
	step6: if count = 0 then 
	step7: 	Print "number is prime"
	step8: else Print "number is not a prime"
stop

Flowchart
flowchart for given number is a prime number in c

C Programming
//a given number is a prime number or not
#include <stdio.h>

int main() {
    int number,count=0;

    printf("Enter a number: ");
    scanf("%d", &number);
    for (int i = 2; i<= number/2; i++) {
        if (number % i == 0) {
            count++;   // Found a divisor, not prime
            break; 
        }
    }
    if (count == 0) {
        printf("%d is a prime number.\n", number);
    } else {
        printf("%d is not a prime number.\n", number);
    }

    return 0;
}

OUTPUT
Enter a number: 31
31 is a prime number.

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