## INDEX

### Prime number program in c using recursion

C code to check a number is prime number or not by recursion:

#include<stdio.h>

int isPrime(int,int);

int main(){

int num,prime;

printf("Enter a positive number: ");
scanf("%d",&num);

prime = isPrime(num,num/2);

if(prime==1)
printf("%d is a prime number",num);
else
printf("%d is not a prime number",num);

return 0;
}

int isPrime(int num,int i){

if(i==1){
return 1;
}else{
if(num%i==0)
return 0;
else
isPrime(num,i-1);
}
}

Sample output:

Enter a positive number: 13
13 is a prime number

C code to check a number is prime number or not without recursion:

#include<stdio.h>

int isPrime(int);

int main(){

int num,prime;

printf("Enter a positive number: ");
scanf("%d",&num);

prime = isPrime(num);

if(prime==1)
printf("%d is a prime number",num);
else
printf("%d is not a prime number",num);

return 0;
}

int isPrime(int num){

int i=2;

while(i<=num/2){
if(num%i==0)
return 0;
else
i++;
}

return 1;
}

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