Figure 4.7 Program for Water-Bill Problem /* * Computes and prints a water bill given an unpaid balance and previous and * current meter readings. Bill includes a demand charge of \$35.00, a use * charge of \$1.10 per thousand gallons, and a surcharge of \$2.00 if there is * an unpaid balance. */ #include #define DEMAND_CHG 35.00 /* basic water demand charge */ #define PER_1000_CHG 1.10 /* charge per thousand gallons used */ #define LATE_CHG 2.00 /* surcharge assessed on unpaid balance */ /* Function prototypes */ 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 - meter reading from previous quarter in thousands of gallons */ int current; /* input - meter reading from current quarter */ double unpaid; /* input - unpaid balance of previous bill */ double bill; /* output - water bill */ int used; /* thousands of gallons used this quarter */ double use_charge; /* charge for actual water use */ double late_charge; /* charge for non-payment of part of previous balance */ /* Display user instructions. */ instruct_water(); /* Get data: unpaid balance, previous and current meter readings. */ printf("Enter unpaid balance> \$"); scanf("%lf", &unpaid); printf("Enter previous meter reading> "); scanf("%d", &previous); printf("Enter current meter reading> "); scanf("%d", ¤t); /* 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); } /* * Displays user instructions */ void instruct_water(void) { printf("This program 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 "); printf("and current meter readings\n"); printf("on separate lines after the prompts.\n"); printf("Press or after "); printf("typing each number.\n\n"); } /* * Computes use charge * Pre: previous and current are defined. */ double comp_use_charge(int previous, int current) { int used; /* gallons of water used (in thousands) */ double use_charge; /* charge for actual water use */ used = current - previous; use_charge = used * PER_1000_CHG; return (use_charge); } /* * Computes late charge. * Pre : unpaid is defined. */ double comp_late_charge(double unpaid) { double late_charge; /* charge for non-payment of part of previous balance */ if (unpaid > 0) { late_charge = LATE_CHG; /* Assess late charge on unpaid balance. */ } else { late_charge = 0.0; } return (late_charge); } /* * Displays late charge if any and bill. * Pre : late_charge, bill, and unpaid are defined. */ 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); }