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C Program to find Prime Number using UDF, also find Prime Numbers upto a limit in C Language

C Program to find Prime Number using UDF, also find Prime Numbers upto a limit in C Language:

Example 1 : C Program to find prime number using user defined function :-

#include<stdio.h>
#include<conio.h>

int primeNumber(int); /* function declaration or prototype, int arg int returns */

void main()
{

int num,prime;
clrscr();

printf("Enter an integer Number :");
scanf("%d",&num);

prime = primeNumber(num); /* function call here with Actual Parameter num, rtns integer value and assigning to the var prime */

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

getch();
}

int primeNumber(int n) /* function definition with Formal Parameter n and returns an integer */
{

int i;

for( i=2 ; i<=n/2 ; i++)
{
if(n%i==0)
return 0;
}

return 1;
}

/* prime number 3,7,11,17.... */

Example 2 : C Program to find prime numbers upto a limit using user defined function :-

#include<stdio.h>
#include<conio.h>

int primeNumber(int);

void main()
{

int num,lmt;
clrscr();

printf("Enter a limit :");
scanf("%d",&lmt);

for(num=3 ; num <= lmt ; num++)
{
if(primeNumber(num)==1)
{
printf("\n%d",num);
}
}
getch();
}

int primeNumber(int n)
{

int i;

for( i=2 ; i<=n/2 ; i++)
{
if(n%i==0)
return 0;
}

return 1;
}


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