To convert decimal to binary:
#include<stdio.h>
#include<conio.h>
void main()
{
int num,i,j,val,arr[8]={0,0,0,0,0,0,0};
clrscr();
printf("enter the number");
scanf("%d",&num);
while(num>1)
{
i=1;
j=0;
while (i<num)
{
i=i*2;
j=j+1;
}
arr[8-j]=1;
val=i/2;
num=num-val;
}
if(num==1)
arr[7]=1;
for(j=0;j<8;j++)
printf("%d",arr[j]);
getch();
}