# C++ Notes: Example - Celsius to Fahrenheit

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    // basics/c2f.cpp - Convert Celsius to Fahrenheit
    // Fred Swartz, 2003-10-26                 // (1)

    #include <iostream>                        // (2)
    using namespace std;                       // (3)

    int main() {                               // (4)
        float celsius;                         // (5)
        float fahrenheit;

        cout << "Enter Celsius temperature: "; // (6)
        cin >> celsius;
        fahrenheit = 1.8 * celsius + 32;
        cout << "Fahrenheit = " << fahrenheit << endl;

        system("PAUSE");  // only Dev-C++      // (7)
        return 0;                              // (8)
    }
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### Notes

1. Comments at the beginning should include the following.
   - Directory and filename.
   - Brief statement of what the program does.
   - Your name.
   - Date
2. `#include` statements make standard libary functions available.
3. The `using namespace std` statement allows access to standard library names (eg, `cin` and `cout`) without a prefix (`std::cin` and `std::cout`).
4. Execution of every program starts in the `main()` function. There is an alternate way to declare `main`, but we will use this simple style.
5. Local variables are declared at the beginning of every function.
6. The computation is often a variation of read-process-write.
7. This system call is only necessary for DevC++ users to keep the console window from closing when the program terminates. It is NOT standard C++.
8. The `main()` function is declared to return an int, therefore it must return some integer value. Zero is commonly used to indicate that the program terminated successfully, but the system normally ignores this number.