CODEWITHSUNDEEP
cbinarylong-integer
rishran
rishran

Reputation: 660

Converting an Unsigned Long to Binary in C

I am trying to convert an unsigned long to binary in C.

char* long_to_binary(unsigned long k)

{
        static char c[65];
        c[0] = '\0';

        unsigned long val;
        for (val = ULONG_MAX; val > 0; val >>= 1)
        {   
            strcat(c, ((k & val) == val) ? "1" : "0");
        }
        return c;
    }

What am I doing wrong here? It prints out the incorrect values. I tried printing out val and instead of printing the base2 values are off by one. So it prints like 3 7 15 .... I tried initialising the value to ULONG_MAX+1 instead of ULONG_MAX but then it doesn't even enter the loop.

Any ideas why this is happening?

Thanks in advance!

Upvotes: 1

Views: 6752

Answers (1)

dbush
dbush

Reputation: 223917

You're initializing val to have all bits set. So when you apply the &, the result of the comparison will be false unless k has all bits set.

You only want one bit set in val, and you need to start with the highest bit. So initialize it like this:

for (val = 1UL << (sizeof(unsigned long)*8-1); val > 0; val >>= 1) {

Then when you call it like this:

printf("binary=%s\n",long_to_binary(0x12345678));

You get this:

binary=0000000000000000000000000000000000010010001101000101011001111000

Upvotes: 3

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