Program for water bill Problem

/*program for water bill problem*/

#include<stdio.h>

#define DEMAND_CHG 35.00 /*basic waterdemand charge*/

#define PER_1000_CHG 1.10 /*charge per thousand gallons used */

#define LATE_CHG 2.00 /* surcharge assessed on unpaid balance */


/*Function prototype*/

void instruct_water(void);

double comp_use_charge(int previous, int current);

double comp_late_charge(double unpaid);

void display_bill(double late_charge, double bill, double unpaid);

int
main(void)
{

int previous; /*input - matter reading from previous quarter*/
int current; //input -meter reading from current quarter
double unpaid; //input -unpaid
double bill; //output - water bill
int used;
double use_charge;
double late_charge;

//display user instruction.

instruct_water();

/*Get data: unpaid balance, previous and current meter reading*/

printf("Enter unpaid balance> $");
scanf("%lf", &unpaid);
printf("Enter previous meter reading> ");
scanf("%d",&previous);
printf("Enter current meter reading>");
scanf("%d",&current);

//compute use charge
use_charge = comp_use_charge(previous,current);
//determine applicable late charge
late_charge = comp_late_charge(unpaid);

//figure bill
bill = DEMAND_CHG + use_charge + unpaid + late_charge;

//print bill
display_bill(late_charge, bill,unpaid);

return (0);

}


/*
*Display user instructions
*/

void instruct_water(void)
{
printf("This problem figures a water bill");
printf("based on the demand charge\n");
printf("($%.2f) and a $%.2f per 1000", DEMAND_CHG,PER_1000_CHG);
printf("gallons use charge.\n\n");
printf("A $%.2f surcharge is added to ", LATE_CHG);
printf("accounts with an unpaid balance.\n");
printf("\nEnter unpaid balance, previous.\n");
printf("and current meter readings\n");
printf("on separate lines after the prompts. \n");
printf("Press<return> or <enter>after");
printf("typing each number.\n\n");
}


/*
*
* computes use charge
*/

double
comp_use_charge(int previous,int current)
{
int used; //gallons of water used
double use_charge;
used = current - previous;
use_charge = used*PER_1000_CHG;
return (use_charge);
}

/*
*computes late charge
*/

double
compu_late_charge(double unpaid)
{
double late_charge;
if(unpaid>0)
late_charge = LATE_CHG;
else
late_charge = 0.0;
return (late_charge);
}

/*
*
*Displays late charge if any and bill,
* pre: late charege
*/

void display_bill(double late_charge, double bill, double unpaid)
{
if(late_charge > 0.0) {
printf("\nBill includes $%.2f late charge",late_charge);
printf("on unpaid balance of $%.2f\n",unpaid);
}
printf("\nTotal due = $%.2f\n",bill);
}





4.5 Deciscion Steps in Algorithms

page 170