b_2_d.c

// program to convert decimal number into binary and binary into decimal number
#include<stdio.h>
void binary(int n)
{
    int rem;
    if(n<=1)
    {
        printf("%d",n);
        return;
    }
    rem=n%2;
    binary(n/2);
    printf("%d",rem);
}
int main()
{
    int n,c,d=0,b=1,r;
    printf("1. For decimal to binary\n");
    printf("2. for binary to decimal\n");
    scanf("%d",&c);
    printf("enter number to convert\n");
    scanf("%d",&n);
    if(c==1)
    {
        if(n<0)
        {
            printf("not possible\n");
        }
        else
        {
            printf("The decimal -> binary is ");
            binary(n);
        }
    }
    else if(c==2)
    {
        while(n>0)
        {
            r=n%10;
            d=d+(b*r);
            n=n/10;
            b=b*2;
        }
        printf("The binary -> decimal is %d\n",d);
    }
}