C-Program for Binary to Decimal Conversion

#include<stdio.h>
#include<stdlib.h>
main()
{
int b,d,z,r,t;
printf("Enter the Binary Number\t");
scanf("%d",&b);
t=b;
z=1;
d=0;
if(b==0)
{
printf("Decimal Equivalant of %d is 0",b);
exit(0);
}
while(b>0)
{
r=b%10;
if(r>1)
{
printf("\n Invalid Entry");
exit(0);
}
d=d+(z*r);
z=z*2;
b=b/10;
}
printf("Decimal Equivalant of %d is\t%d",t,d);
} 

output