Thread: Functions and Encapsulation

You need to format your program properly by the use of appropriate indentation and other whitespace, e.g.,

Code:

/* This program converts temperatures from Celsius to Fahrenheit,
   using the standard Celsius-to-Fahrenheit conversion
   formula.
   Entering any value less than -273.15 Celsius (approx. absolute
   zero) terminates the program.
   Input: tempCelsius
   Output: tempFahrenheit
--------------------------------------------------------------------*/

#include <iostream>

using namespace std;

double celsiusToFahrenheit(double tempCels); // function prototype

int main()
{
    cout << "Program to convert Celsius temperatures to Fahrenheit.\n";
    double tempCelsius, // Celsius temperature
    tempFahrenheit; // Fahrenheit temperature
    cout << "\nEnter a Celsius temperature (< -273.15 to stop): ";
    cin >> tempCelsius;
    while (tempCelsius >= -273.15)
    {
        tempFahrenheit = celsiusToFahrenheit(tempCelsius);
        cout << tempCelsius << " degrees Celsius is equivalent to "
             << tempFahrenheit << " degrees Fahrenheit\n";
        cout << "\nEnter a Celsius temperature (< -273.15 to stop): ";
        cin >> tempCelsius;
    }
}

double celsiusToFahrenheit(double tempCels) // function definition
{
    return 1.8 * tempCels + 32;
}

Originally Posted by Alienspecimen

would like to understand how the function's argument "tempCelsius" is passed onto the function and most of all why we need to define the parameter "tempCels" which uses the argument's value. What is the difference between the two

The actual argument is the object that is passed to the function call at the place of the call. The formal parameter is the variable is that declared to correspond to the various actual arguments, being in the scope of the function's body rather than in the scope of the place of the call.

Originally Posted by Alienspecimen

why in the function definition (green)we cant just write:

double celsiusToFahrenheit(double tempCelsius)

as defined in red previously?

It looks like you have a serious typo error in your question that makes it hard to understand because as written, your question does not make sense.

Originally Posted by Alienspecimen

What is the need to define "tempCels" and how does the function definition know to take the value of "tempCelsius and place it into tempCels"?

You need to declare tempCels so that the function has a parameter such that at the call site, a value can be passed to the function that will correspond to this parameter. The function definition "knows" that the argument corresponds to the parameter by position, i.e., the first argument in the function call corresponds to the first parameter in the function definition, the second argument corresponds to the second parameter, etc.