C language program to find out the factorial of an integer by calling a function.

#include<stdio.h>

void main()

{

          long int n;

          long int fact(long int n);

          clrscr();

          printf(" Enter a number: ");

          scanf("%ld",&n);

          printf(" Factorial of %ld is %ld",n,fact(n));

          getch();

}

long int fact(long int i)

{

          int fct=1;

          for(;i>=1;i--)

          fct*=i;

          return fct;

}

C language program to find out the factorial of an integer by using "while" loop.

#include<stdio.h>

main()

{

          double n,ans=1;

          clrscr();

          printf(" Enter a number\n to find factorial of it : ");

          scanf("%lf",&n);

          while (n>1.)

          {

          ans*=n;

          --n;

          }

          printf(" answer = %.2lf",ans);

          getch();

}

C language program to find Prime Number.

#include<stdio.h>

#include<math.h>

void main()

{

          int num,i,is_prime=0;

          clrscr();

          printf(" Give a number : ");

          scanf("%d",&num);

          for (i=2;i<=sqrt(num);i++)

          {

          if (num%i==0)

          {

          is_prime=1;

          break;

          }

          }

          if (is_prime==1)

          printf(" Not prime number");

          else

          printf(" Prime number");

          getch();

}

A C language program to print Triangle of asterisks (*).

#include<stdio.h>

void draw_j(void);

void main()

{

          clrscr();

          draw_j();

          getch();

}

void draw_j(void)

{

          int a,s;

          for(a=5;a>=1;a--)

          {

          s=1;

          while (s<=a)

          {

          printf("*");

          s++;

          }

          printf("\n");

          }

}

OUTPUT:

********

*******

******

*****

****

***

**

*

A C language program that promotes the user to enter a number and then reverse it.

For example, if the user enters 5143, the function would reverse it so that it becomes 3415.

#include<stdio.h>

void main ()

{

          int num=0;

          clrscr();

          printf(" Enter a number to reverse : ");

          scanf("%d",&num);

          printf(" Reverse of %d is %d\n",num,reverse(num));

          getch();

}

int reverse(int num)

{

          int res=0,temp=num,k,a=0,i;

          /* finds the number or digits*/

          for(;temp/10!=0;temp/=10)

          a++;

          for(;num/10!=0;)

          {

          k=num%10;

          for(i=0;i<a;i++)

          {

          k*=10;

          }

          num/=10;

          a--;

          res+=k;

          if (num<10)

          res+=num;

          }

          return res;

}