#include<stdio.h>
#include<string.h>
int hexadecimal_decimal(char hex[100])
{
     int i = 0, val,decimal,len;
    decimal = 0;
     len = strlen(hex);
     len--;
     for(i=0; hex[i]!='\0'; i++)
     {
        if(hex[i]>='0' && hex[i]<='9')
        {
            val = hex[i] - 48;
        }
        else if(hex[i]>='a' && hex[i]<='f')
        {
            val = hex[i] - 97 + 10;
        }
        else if(hex[i]>='A' && hex[i]<='F')
        {
            val = hex[i] - 65 + 10;
        }

        decimal += val * pow(16, len);
        len--;
        return decimal;
    }

}

int  octaldecimal(int c)
{
   int temp=0,i=0,mod;
   while(c!=0)
    {
        mod=c%10;
        temp=temp+mod*pow(8,i);
        c=c/10;
        i++;
    }
    return temp;
}


int  decimal(int c)
{
   int temp=0,i=0,mod;
   while(c!=0)
    {
        mod=c%10;
        temp=temp+mod*pow(2,i);
        c=c/10;
        i++;
    }
    return temp;
}

void hexadecimal(int a)
{
  int  i=0,count=0,arr[1000];
  while(a!=0)
    {
        arr[i]=a%16;
        count+=1;
        a=a/16;
        if(arr[i]<10)
        {
            arr[i]=48+arr[i];
        }
        else if(arr[i]>=10)
        {
            arr[i]=55+arr[i];
        }
        i++;

    }
    for(i=count-1;i>=0;i--)
    {
        printf("%c",arr[i]);
    }
}


void binary(int c)
{
    int count=0,i=0,arr[1000];
     while(c!=0)
    {
        arr[i]=c%2;
        count+=1;
        c=c/2;
        i++;
    }
    for(i=count-1;i>=0;i--)
    {
        printf("%d",arr[i]);
    }
}


int main()
{
    int a,b,c,x;
    printf("\nEnter 0 for goto menu:\n");
    printf("\n*************************\n");
    printf("*************************\n");
    scanf("%d",&a);
    printf("\n*************************\n");
    printf("*************************\n");
    printf("                         \n");


    if(a==0)
    {
        printf("//Enter 1   for Decimal to Binary      :\t      //Enter 2   for Octal to Binary       :\n");
        printf("//Enter 3   for Decimal to Octal       :\t      //Enter 4   for Octal to Decimal      :\n");
        printf("//Enter 5   for Decimal to Hexadesimal :\t      //Enter 6   for Octal to Hexadesimal  :\n");
        printf("                                        \t                                             \n");
        printf("                                        \t                                             \n");
        printf("//Enter 7   for Binary  to Decimal     :\t      //Enter 8   for Hexadesimal to Decimal:\n");
        printf("//Enter 9   for Binary  to Octal       :\t      //Enter 10  for Hexadesimal to Binary :\n");
        printf("//Enter 11  for Binary  to Hexadesimal :\t      //Enter 12  for Hexadesimal to Octal  :\n");
        printf("                                                                                       \n");


        printf("***\n");
        printf("Enter your number:  ");
        scanf("%d",&b);
        printf("***\n");

        if(b==1)
        {
            printf("Enter Decimal number:\n");
            printf("                         \n");
            scanf("%d",&c);
            printf("                         \n");
            printf("The Binary from of %d is :\n",c);
            printf("                         \n");
            binary(c);
            printf("                         \n");
        }
        else if(b==2)
        {
            printf("Enter Octal number:\n");
            printf("                         \n");
            scanf("%d",&c);
            printf("                         \n");
            x=octaldecimal(c);
            printf("The Binary from of Octal number is: ");
            binary(x);
            printf("                         \n");
        }

        else if(b==3)
        {
            printf("Enter Decimal number:\n");
            printf("                         \n");
            scanf("%d",&c);
            printf("                         \n");
            printf("The Octal from of Decimal number is: %o\n",c);
            printf("                         \n");
        }

        else if(b==4)
        {
            printf("Enter Octal number:\n");
            printf("                         \n");
            scanf("%d",&c);
            printf("                         \n");
            x=octaldecimal(c);
            printf("The Decimal from of Octal number is: %d",x);
            printf("                         \n");
        }

        else if(b==5)
        {
            printf("Enter Decimal number:\n");
            printf("                         \n");
            scanf("%d",&c);
            printf("                         \n");
            printf("The Hexadecimal from of Decimal number is: ");
            hexadecimal(c);
            printf("                         \n");
        }

        else if(b==6)
        {
            printf("Enter Octal number:\n");
            printf("                         \n");
            scanf("%d",&c);
            printf("                         \n");
            x=octaldecimal(c);
            printf("The Hexadecimal from of Octal number is: ");
            hexadecimal(x);
            printf("                         \n");

        }

        else if(b==7)
        {
             printf("Enter Binary number:\n");
             printf("                         \n");
             scanf("%d",&c);
             printf("                         \n");
             printf("The Decimal from of Binary number is: %d\n",decimal(c));
             printf("                         \n");

        }
        else if(b==8)
        {
            printf("Enter Hexadecimal number:\n");
            printf("                         \n");
            char str[100];
            scanf("%s",str);
            printf("                         \n");
            x=hexadecimal_decimal(str);
            printf("The Decimal from of hexadecimal is %d",x);
            printf("                         \n");
        }

        else if(b==9)
        {
            printf("Enter Binary number:\n");
            printf("                         \n");
            scanf("%d",&c);
            printf("                         \n");
            x=decimal(c);
            printf("The Octal from of Binary number is: %o\n",x);
            printf("                         \n");
        }
        else if(b==10)
        {
            printf("Enter Hexadecimal number:\n");
            printf("                         \n");
            char str[100];
            scanf("%s",str);
            printf("                         \n");
            x=hexadecimal_decimal(str);
              printf("The Binary from of Hexadecimal number is :\n");
            printf("                         \n");
            binary(x);
            printf("                         \n");


        }
        else if(b==11)
        {
            printf("Enter Binary number:\n");
            printf("                         \n");
            scanf("%d",&c);
            printf("                         \n");
            x=decimal(c);
            printf("The Hexadecimal from of Binary number is: ");
            hexadecimal(x);
            printf("                         \n");
        }
        else if(b==12)
        {
            printf("Enter Hexadecimal number:\n");
            printf("                         \n");
            char str[100];
            scanf("%s",str);
            printf("                         \n");
            x=hexadecimal_decimal(str);
            printf("The Octal from of Hexadecimal number is %o",x);
            printf("                         \n");

        }


    }
    return 0;

}