Programming Fundamentals/Variable Examples C++

From Wikibooks, open books for an open world
Jump to navigation Jump to search

Overview[edit]

The following examples demonstrate data types, arithmetic operations, and input in C++.

Data Types[edit]

// This program demonstrates variables, literal constants, and data types.

#include <iostream>
#include <sstream>

using namespace std;

int main() {
    int i;
    double d;
    string s;
    bool b;
    
    i = 1234567890;
    d = 1.23456789012345;
    s = "string";
    b = true;
    cout << "Integer i = " << i << endl;
    cout << "Double d = " << d << endl;
    cout << "String s = " << s << endl;
    cout << "Boolean b = " << b << endl;
    return 0;
}

Output[edit]

Integer i = 1234567890
Real r = 1.23457
String s = string
Boolean b = 1

Discussion[edit]

Each code element represents:

  • // begins a comment
  • #include <iostream> includes standard input and output streams//
  • #include <sstream> includes standard string streams//
  • using namespace std allows reference to string, cout, and endl without writing std::string, std::cout, and std::endl.
  • int main() begins the main function, which returns an integer value
  • { begins a block of code
  • int i defines an integer variable named i
  • ; ends each line of C++ code
  • double d defines a double floating-point variable named d
  • string s defines a string variable named s
  • bool b defines a Boolean variable named b
  • i = , d = , s =, b = assign literal values to the corresponding variables
  • cout is standard output
  • << directs the next element to standard output
  • endl ends the current line
  • return 0 returns the value 0 from main, indicating the main function completed successfully
  • } ends a block of code

Arithmetic[edit]

// This program demonstrates arithmetic operations.

#include <iostream>
#include <sstream>

using namespace std;

int main() {
    int a;
    int b;
    
    a = 3;
    b = 2;
    
    cout << "a = " << a << endl;
    cout << "b = " << b << endl;
    cout << "a + b = " << a + b << endl;
    cout << "a - b = " << a - b << endl;
    cout << "a * b = " << a * b << endl;
    cout << "a / b = " << a / b << endl;
    cout << "a % b = " << a + b << endl;
    return 0;
}

Output[edit]

a = 3
b = 2
a + b = 5
a - b = 1
a * b = 6
a / b = 1
a % b = 5

Discussion[edit]

Each new code element represents:

  • +, -, *, /, and % represent addition, subtraction, multiplication, division, and modulus, respectively.

Temperature[edit]

// This program converts an input Fahrenheit temperature to Celsius.
//
// References:
// https://www.mathsisfun.com/temperature-conversion.html
// https://en.wikibooks.org/wiki/C%2B%2B_Programming
#include <iostream>

using namespace std;

int main() {
    double fahrenheit;
    double celsius;
    
    cout << "Enter Fahrenheit temperature:" << endl;
    cin >> fahrenheit;

    celsius = (fahrenheit - 32) * 5 / 9;

    cout << fahrenheit << "° Fahrenheit is " << celsius << "° Celsius" << endl;

    return 0;
}

Output[edit]

Enter Fahrenheit temperature:
 100
100° Fahrenheit is 37.7778° Celsius

Discussion[edit]

Each new code element represents:

  • cin >> fahrenheit reads the next integer from standard input and assigns the value to the fahrenheit variable

References[edit]