CSC133 Intro to CS in C++: Function Example

Sample Program: Using Functions

//  this program calculates the miles per gallon and total cost
//  of a car trip

#include <iostream.h>
#include <iomanip.h>

//  function prototypes
float mpg(int,float);
float tripcost(float,float,float);
void heading();

int main()
{
   int milesdriven;
   float costgallon;
   float costtolls;
   float gasused;
   float totalcost;

//  call the heading function
   heading();

//  set up output to print float values with one decimal place
   cout << setiosflags(ios::fixed);
   cout << setiosflags(ios::showpoint);
   cout << setprecision(1);

//  prompt for the number of miles driven and the amount of gas used
   cout << "Enter the number of miles driven: ";
   cin >> milesdriven;
   cout << "Enter the gallons of gas used: ";
   cin >> gasused;

//  call the mpg function to calculate miles per gallon and print the
//  value returned
   cout << "On this trip you got " << mpg(milesdriven,gasused)
        << " miles per gallon.\n";

//  prompt for the cost of a gallon of gas and the cost of tolls
   cout << "Enter the cost paid for a gallon of gas: ";
   cin >> costgallon;
   cout << "Enter the cost of tolls on the trip: ";
   cin >> costtolls;

//  change output to print floats with two decimal places
   cout << setprecision(2);

//  call totalcost to compute the cost of the trip, then print
   totalcost = tripcost(costgallon,gasused,costtolls);
   cout << "The total cost of the trip was " << totalcost << endl;
}

//  print a heading in the output
void heading()
{
   cout << "Sample Program for Class Demonstration\n";
   cout << "Calculate gas mileage and cost for a trip\n\n";
}

//  calculate and return the miles per gallon
float mpg(int milesdriven,float gasused)
{
   return milesdriven / gasused;
}

//  calculate and return the cost of the trip (cost of gas + cost of tolls)
float tripcost(float costgallon,float gasused,float costtolls)
{
   return costgallon * gasused + costtolls;
}

Sample Execution:

Sample Program for Class Demonstration
Calculate gas mileage and cost for a trip

Enter the number of miles driven: 128
Enter the gallons of gas used: 4.8
On this trip you got 26.7 miles per gallon.
Enter the cost paid for a gallon of gas: 1.39
Enter the cost of tolls on the trip: 5.50
The total cost of the trip was 12.17