Some Important Program

Number conversion (binary,decimal,octal,hexadecimal)

#include<stdio.h>
#include<conio.h>
void main()
{
    char base16[16]={'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
    long num;
    long cnum[68];
    int base,number,i,j;
    clrscr();
    printf("\nEnter a decimal number to convert : ");
    scanf("%ld",&num);
    printf("\nEnter base for convert : 2(for binary),8(for octal),16(for hexadecimal) : ");
    scanf("%d",&base);
    i=0;
    while(num!=0)
    {
         cnum[i]=num%base;
         num=num/base;
         i++;
    }
    i=i--;

    printf("\nThe number in your base is : ");
    for(i=i;i>=0;i--)
    {
         number=cnum[i];
         printf("%c",base16[number]);
    }
    getch();
}

GCD by recurtion
#include<stdio.h>
#include<conio.h>
int gcd(int m , int n)
{
    if(m==0)
        return n;
    if(n==0)
        return m;
    return gcd(n, m%n);
}
void main()
{
    int m,n;
    printf("enter m,n value:");
    scanf("%d%d",&m,&n);
    printf("the gcd is:%d",gcd(m,n));
    getch();
} 

Run this and try to understand this  

#include<stdio.h>
#include<conio.h>
int nonprime(int p);
void main()
{
    long int i,j,n,a[5];
    int count=0;
   
    for(i=10000;i<=99999;i++)
    {
         n=i;j=0;
         while(n!=0)
         {
        a[j]=n%10;
        n=n/10;
        j++;
         }
         if((a[4]%2==0) && (a[3]%2!=0) && (nonprime(a[2])) && (a[1]!=a[2]!=a[3]!=a[4]) && (a[0]!=a[2]!=a[3]!=a[4]))
         {
         count=count+1;
         }
         else
         count=count+0;
    }
    printf("The number is %d .",count);
   
}
int nonprime(int p)
{
    int j;
    for(j=2;j<=p;j++)
    {
       if(p%j==0)
           break;
       if(p==j)
          return 0;
       else
          return 1;
    }
}