Okay, I got the message, I will post more stuff in the every so lively C forum!!!!

Not better, but cute, create your own display window with a Windows message box ...
// use a message box to display console output
// compile as GUI
#include <windows.h>
#include <string.h>...

Are you trying to printf() a double into an integer format specifier %d?
You could cast to an integer, but it looks like you are flirting with the integer size limits.

You are declaring functions residential_rate(), commercial_rate(), industrial_rate() also as floats of the same name in function main(). Remove those variables and it will work!

Oops, I was too...

One mild problem from past experience, if the users enters a floating point number, this loop spins out of control. Give it a try, it's good exercise.

Here is a small project, go through all the functions listed at:
http://www.phim.unibe.ch/comp_doc/c_manual/C/FUNCTIONS/funcref.htm
and come up with a code sample of a practical application for...

When in doubt, use the old workhorse printf(). I have played around with manipulators like cout << setfill('0') << setw(8) << d1;
with results that cause only consternation. The old printf()...

Console debugging has problems with old Windows and Dev C++ versions. You should be okay with version 4.9.9.0
Here is the poop:
Debugging with Dev C++:
Make sure you are using a project!
Go to...

Convert a decimal (denary) integer to a binary string. An exercise in do ... while and while loops.

double fmod(double x, double y) is a function, so you have to rewrite your code a little. It returns the remainder of the division x / y. Make sure to #include <math.h>

Here is some C code that might help you get started.
// A linear list of data accessed first in, first out (FIFO) is called a QUEUE.
// Pelles C (vegaseat)

#include <stdio.h> // in/out...