Using long and arrays in C++ - c++

Question

I've been working on a program that converts numbers into binary. As you can see my program here, I've written so that it can scale for larger numbers then a traditional binary code, such as 2 lines (16-bits) for numbers bigger then 255. However, going larger requires long instead of int, but that doesn't seem to be playing well, producing output such as this. Would anyone mind helping me change the program to use long? Or would it require a fundamental change in the code instead of some minor edits?
#include <iostream>
#include <math.h>
using namespace std;
int main(int argc, char **argv)
{
int j=0;
int c=8;
long a = 1;
int i=1;
cin >> a;
while (a >= (pow(2,c))) {
c = c+8;
i++;
}
long block[i*8];
for (long tw;tw<(i*8);tw++)
{
block[tw] = 0;
}
j=((i*8)-1);
long b = 0;
while (j != -1)
{
if (b+(pow(2,j))<=a)
{
block[j]=1;
b=b+(pow(2,j));
}
j--;
}
long q=0;
cout << endl;
int y=1;
long z = 0;
for (y;y<=i;y++) {
for (z;z<8;z++) {
cout << block[z+q];
}
cout << endl;
z = 0;
q = q + (8*y);
}
}

Answer 1

You are making your code far more complicated than it needs to be. This will print out a single 32-bit integer in binary:
const unsigned int bit_count = sizeof(int) * 8 - 1;
int a;
std::cin >> a;
for (unsigned int i = bit_count; i > 0; --i)
{
unsigned int t = (1 << i);
std::cout << (a & t ? "1" : "0");
}
std::cout << (a & 1 ? "1" : "0");
std::cout << std::endl;
If you want to block it off by ranges to make it easier to read, you simply need to place range on the loop (or move it to a function that takes a range).

Answer 2

Why not something simple like this? You could store the intermediate bits in an array or a string instead of using cout.
int convert(long n)
{
long k=1;
while(k<n)//find the most significant bit
{
k*=2;
}
if(k>n)//fix the overshoot
{
k/=2;
}
while(k>0)
{
if(int(n/k)%2==0)
{
cout<<0;//find the (next) most
}
else
{
cout<<1;//significant binary digit
}
k/=2;//go to the next column to the right and repeat
}
}

Answer 3

For a bit more flexibly, here's another way to do it with templates. Template instantiations with signed types are omitted intentionally due to extension issues.
template <typename T>
void print_binary(const T input, const short grouping = 4)
{
unsigned int bit_count = sizeof(T) * 8;
T nth_bit = 1 << (bit_count - 1);
for(int i = 0; i < bit_count; i++, nth_bit >>= 1 )
{
cout << (input & nth_bit ? "1" : "0");
if( i % grouping == grouping-1 ) // print binary in groups
cout << ' ';
}
cout << endl;
}
template <>
void print_binary<signed>(const signed input, const short grouping);
template <>
void print_binary<signed short>(const signed short input, const short grouping);
template <>
void print_binary<signed long>(const signed long input, const short grouping);
template <>
void print_binary<signed char>(const signed char input, const short grouping);