Jun 29, 2020

C program to check given number is prime or not using function

Ex: write a C program to check given number is prime or not using function. How to write a C program to check given number is prime or not using function. C program to check given number is prime or not using function.


Input from user:

Enter the number: 5

Expected output:

Given number is prime number.





Step by Step logic of the given program:


1. First declare function give it meaningful name prime().

2. Inside the main() accept input (number) from user declare varible say no.

3. Using if statement call prime function- if(prime(no)). after that inside the if statement print given number is prime otherwise print number is not prime. (If returned value is 1(true) then it will print number is prime otherwise it will execute else block

4. After that inside the prime() we will use following prime numbers logic-
for(i=1;i<=no;i++)
{
if(no%i==0)
{
count++;
}
}

Here, count will be 2 only if number is prime.


5. In the last check count is 2 or not using- if(count==2) 
If it's true return 1 otherwise return 0;





Program:

#include<stdio.h>
int prime(int);
int main()
{
int no;

printf("Enter the number\n");
scanf("%d",&no);

if(prime(no))
    {
    printf("Given number is prime number");
    }
    else
    {
    printf("Given number is not prime number");
    }
}
int prime(int no)
{
int count=0,i;

for(i=1;i<=no;i++)
{
if(no%i==0)
{
count++;
}
}
if(count==2)
{
return 1;
}
else
{
return 0;
}
}


Above program shows the following output:




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