Base conversion in C

#include <stdio.h>
#include <math.h>

void convert_base(double x, double b)
{
	double y, z;
	int digit, i, j = 0, k;

/* Find the terms in power series expansion with base power > 0 */

	z = x;
	while(z >= 1)
	{

/* Compute largest power of base which divides x  giving a value >= b*/

		y = z;
		digit = y;
		i = 0;
		while(digit >= b)
		{
			y = y / b;
			digit = y;
			i++;
			//printf("y = %lf\n", y);
		}

		//printf("i = %d\n", i);
		//printf("digit = %d\n", digit);

/* Subtract off this term in series expansion */

		z = z - (digit * pow(b, i));

		//printf("z = %lf\n", z);

/* Fill in digits in between the last calculated digit and this calculated digit */

		if((abs(i - j) > 1) && (j != 0))
		{
			for(k = 1; k < abs(i - j); k++)
			{
				printf("0");
			}
		}
		printf("%d", digit);

		j = i;

	}

	if(j != 0)
	{
		for(k = j; j > 0; j--)
		{
			printf("0");
		}
	}

	printf(".");

/* Find the terms in the power series expansion with base power < 0 */

	while((z > 0) && (z <= 1) && (i > -6))
	{

/* Compute smallest power of base which multiplies x giving a value >1 */

		y = z;
		digit = y;
		i = 0;
		while(digit < 1)
		{
			y = y * b;
			digit = y;
			i--;
			//printf("y = %lf\n", y);
		}

		//printf("i = %d\n", i);
		//printf("digit = %d\n", digit);

/* Subtract off this term in series expansion */

		z = z - (digit * pow(b, i));

		//printf("z = %lf\n", z);

/* Fill in digits in between the last calculated digit and this calculated digit */

		if(abs(i - j) > 1)
		{
			for(k = 1; k < abs(i - j); k++)
			{
				printf("0");
			}
		}
		printf("%d", digit);

		j = i;
	}

	if(z == 0)
	{
		printf("000");
	}

	printf("...\n");
}

int main(void)
{
	double x, b;

	printf("Enter a number: x = ");
	scanf("%lf", &x);
	printf("Enter the base for conversion: b = ");
	scanf("%lf", &b);

	printf("(x)_b = %lf = ", x);

	convert_base(x, b);

	return 0;
}

if(j != 0)
	{
		for(k = j; j > 0; j--)
		{
			printf("0");
		}
	}