This program converts decimal to binary numbers. It works for positive integers 0-127. To see how conversions between number systems work, read the post on The Decimal, Binary, Octal & Hexadecimal Number Systems

Executable - Download decimal2binary.exe

Code -

#include<stdio.h>
#include<conio.h>

/* program to convert decimal to binary
- works for positive numbers 0-127 */

int main()
{
    int x, i=0;
    printf("Enter the decimal number\n");
    scanf("%d", &x);
    int y=x;
    int j=0;
    /* this loop gets a count of the number of bigits/remainders */
    while(x!=0)
    {
      i=x%2;
      x=x/2;
      j++;
    }
    x=y;
    int n=0, a[n];
    /* second loop feeds values of bigits to array */
    while(n<j && x!=0)
    {
      i=x%2;
      x=x/2;
      a[n]=i;
      n++;
    }
    n=0;
    printf("The binary equivalent is ");
    /* third loop prints the reversed array */
    while(n<j)
    {
      printf("%d", a[j-(n+1)]);
      n++;
    }
    getch();
    return 0;
}