Problems with accessor and mutator functions of class - c++

Question

I'm trying to write a simple program that takes in a Kelvin temperature input from the user, and output the Farneheit and Celsius conversions of it. However, for a Kelvin input of 273.15, my program keeps outputting strange numbers like "6.95274e-310" for Farenheit and "4.6519e-310" for Celsius. I believe there is a problem with the accessor and mutator functions within the class, but I'm not quite sure what the issue is.
#include <iostream>
using namespace std;
class Temperature{
private:
double Kelvin;
double Celsius;
double Farenheit;
public:
void setKelvin(double);
void setCelsius();
void setFarenheit();
double getKelvin();
double getCelsius();
double getFarenheit();
};
void Temperature::setKelvin(double x){
Kelvin = x;
}
void Temperature::setCelsius(){
Celsius = Kelvin-273.15;
}
void Temperature::setFarenheit(){
Farenheit = (Celsius/(5.0/9))+32;
}
double Temperature::getKelvin(){
return Kelvin;
}
double Temperature::getCelsius(){
return Celsius;
}
double Temperature::getFarenheit(){
return Farenheit;
}
int main(){
cout<<"Enter a temperature in degrees Kelvin: ";
double y;
cin>>y;
Temperature K;
K.setKelvin(y);
cout<<"Temperature after converting to Celsius: ";
cout<<K.getCelsius();
cout<<"Temperature after converting to Farenehti: ";
cout<<K.getFarenheit();
}

Answer 1

Whenever you see weird values like this, it's very likely that these are uninitialized memory (aka garbage). It is data that was written by another application before and not been changed (initialized) by yours. That is why it's very important to always initialize variables.
Built-in types (int, char, double, etc) aren't initialized automatically: that is why you often see statements like int x(0);. Other objects, on the other hand, are initialized via the default constructor. This is why std::string str; doesn't create garbage: an empty std::string is created by std::string::string().
This behavior is clearly demonstrated in your program: Temperature::Celsius and Temperature::Farenheit are never initialized. An easy fix is to add the following lines after K.setKelvin(y):
K.setCelsius();
K.setFarenheit();
Alternative solutions may involve recalculating the Celsius and Farenheit values in their respective getters or systematically "synchronizing" them in the setKelvin method.