while loop in C programing - c

Question

Write a program that contains the loop
while (scanf("%1f", &salary) == 1) {...}
within the body of the loop compute a 17% federal withholding tax and a 3% state withholding tax and print these values along with the corresponding salary. Accumulate the sums of all salaries and taxes printed. Print these sums after the program exits the while loop.
My current code:
float salary, federal_tax, state_tax, salary_after_tax, salary_sum, tax_sum, salary_after_tax_sum;
printf("Enter Salary: $");
while (scanf("%lf", &salary) == 1)
{
salary_sum = salary;
federal_tax = salary*(.17);
state_tax = salary*(.03);
tax_sum = federal_tax + state_tax;
salary_after_tax = salary - federal_tax - state_tax;
salary_after_tax_sum = salary_after_tax;
printf("Salary before tax = %lf", salary);
printf("Federal tax = %lf", federal_tax);
printf("State tax = %lf", state_tax);
printf("Salary after tax = %lf\n", salary_after_tax);
break;
}
printf("total salary before tax = %lf", salary_sum);
printf("total tax = %lf", tax_sum);
printf("total salary after tax = %lf\n", salary_after_tax_sum);
system ("pause");
return 0;
}
For some reason it doesn't work. Any help would be appreciated.

Answer 1

Your scanf specifier is %lf (your problem statement says %1f instead, is that intentional?) and yet you're storing into a float. My scanf(3) says %lf specifies a double.
Incidentally, float has much less precision than many programmers may expect, just about seven digits, so using double instead is probably a good idea for salaries.

Answer 2

You should assign your ..._sum variable to 0 outside the loop, and increment them with += in the loop; what you're doing now instead is reassigning them every time through the loop, and that isn't summing!-)

Answer 3

You lied to the compiler and it got its revenge: the %lf format needs to go with a pointer-to-double, while you provide only a pointer-to-float. This means undefined behavior in C lingo (anything may happen).
Fix your float declarations by turning them into doubles.