Converting base 10 to base 2

Hey guys. I am doing an extra credit assignment where I need to convert any number from 0 to 18,446,744,073,709,551,615. I got down the basic layout to get base 10 into base 2, but backwards. Here is my code:

Code:

---

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a,b;

    printf("BASE 10 TO BASE 2 CONVERTER\n\n");
    printf("Enter the base 10 number you want to convert:");
    scanf("%d", &a);

    while(a!=0)
    {
        b=a%2;
        a=a/2;
        printf("%d", b);
    }
    return 0;
}

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So I have 2 questions.

1. How can I make "printf("%d", b);" to make it actually become a whole number instead of printing each number one by one? Would I use an array? If not an array, how would I reverse the numbers?

2. Which data type can I use to receive such a large input? Would I use an unsigned float maybe?

Storing the result in an array, then printing the array in reverse is one way.

Using recursion to print a/2 before printing a%2 is another way.

> 2. Which data type can I use to receive such a large input? Would I use an unsigned float maybe?
Your max number is a full 64-bit number.
You could try 'unsigned long long int a' with scanf("%ull",&a);

Quote:

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Originally Posted by Salem

Storing the result in an array, then printing the array in reverse is one way.

Using recursion to print a/2 before printing a%2 is another way.

> 2. Which data type can I use to receive such a large input? Would I use an unsigned float maybe?
Your max number is a full 64-bit number.
You could try 'unsigned long long int a' with scanf("%ull",&a);

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How do I assign a value to a certain c[i] array? Also how do would I know how much to assign to the array when declaring it?

So I got the program all set up and it works. But only if I use int. Whenever I used unsigned int or unsigned long long int, the program constantly spits out 0 or 1 on to the screen nonstop. Here is what I have so far:

Code:

---

#include <stdio.h>

int main()
{
    int a, b, d, c[36]={0}, i;
    i=0;


    printf("BASE 10 TO BASE 2 CONVERTER\n\n");
    printf("Enter the base 10 number:");
    scanf("%d", &a);
    d=a;


    while (a!=0)
    {
        b=a%2;
        a=a/2;
        c[i]=b;
        i++;
    }


    printf("\"%d\" in base 10 is equal to \"", d);
    for(i=i-1; i>=0; i--)
        printf("%d", c[i]);
    printf("\" in base 2\n");




    return 0;
}

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The problem I also run into is creating an array using unsigned long long int, then trying to set b, an unsigned long long int, to c[i], which is an unsigned int or whatever.

Also what does recursive mean? I never learned about that.

Well if you made your loop variable unsigned, then it would loop forever, because >= 0 would always be true.

Code:

---

#include <stdio.h>
 
int main()
{
    unsigned int a, b, d, c[36]={0};
    int i;
    i=0;
 
 
    printf("BASE 10 TO BASE 2 CONVERTER\n\n");
    printf("Enter the base 10 number:");
    scanf("%u", &a);
    d=a;
 
 
    while (a!=0)
    {
        b=a%2;
        a=a/2;
        c[i]=b;
        i++;
    }
 
 
    printf("\"%d\" in base 10 is equal to \"", d);
    for(i=i-1; i>=0; i--)
        printf("%d", c[i]);
    printf("\" in base 2\n");
 
 
 
 
    return 0;
}


$ ./a.out
BASE 10 TO BASE 2 CONVERTER

Enter the base 10 number:255
"255" in base 10 is equal to "11111111" in base 2
$ ./a.out
BASE 10 TO BASE 2 CONVERTER

Enter the base 10 number:65536
"65536" in base 10 is equal to "10000000000000000" in base 2

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> Also what does recursive mean? I never learned about that.
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