Variables, types, and input

These are notes from 9 September.

output-examples.cpp

// Any line that starts with double-slash
// is a "comment." -- it is ignored by
// the compiler.
#include <iostream>
using namespace std; // my namespace
int main()
{
    /* Another comment --
       can go for multiple lines */ 
    cout << "Hello again, CS102.\n";
    cout << "This is another stmt."
         << " and more stuff here.\n";
    return 0;
}

variables.cpp

// variables.cpp
#include <iostream>
using namespace std;
int main()
{
    // Variable is a named storage location.
    // Must declare the TYPE of the variable.
    //  (1) int -- an integer (whole number)
    //  (2) double -- a floating-point number
    int x;  // Declare x as an integer
    double y;

    x = 13;  // "x gets the value 13"
    y = 3.1415 * 24;    
 
    cout << "This is an integer: "
         << x << "\n";
    cout << "Your result is:"
         << y << "\n";
                      
    x = 80;                     
    cout << "This is an integer: "
         << x << "\n";
                        
    return 0;
}

temperature.cpp

#include <iostream>
using namespace std;
int main()
{
    double temp_f, temp_c;
    temp_c = 22; // input
    // calculation
    //temp_f = 9*temp_c/5 + 32; // works!
    //temp_f = 9/5*temp_c + 32; // fails!
    //temp_f = 1.8*temp_c + 32; // works
    temp_f = 9.0/5*temp_c + 32; // works!
    // output
    cout << temp_c << "C is "
         << temp_f << "F\n";
    
    return 0;
}

temperature-input.cpp

#include <iostream>
using namespace std;
int main()
{
    double temp_f, temp_c;
    //temp_c = 22; // input
    cout << "Type a temperature in C: ";
    cin >> temp_c;
    // calculation
    temp_f = 9.0/5*temp_c + 32; // works!
    // output
    cout << temp_c << "C is "
         << temp_f << "F\n";
    
    return 0;
}