怎么做的啊用c语言

printf("Enter a binary number
");scanf("%d",&x);
for(x1=x;x;x/=10,t*=2)
n+=x%10*t;

printf("The decimal equivalent of %d is %d
",x1,n);  return 0;
}



#include
int main(void)
{int x,x1,t=1,n=0;

printf("Enter a number:
");scanf("%d",&x);
for(x1=x;x;x/=10)
n+=(x%10==7);

printf("The number %d has %d seven(s) in it
",x1,n);  return 0;
}