Programming Fundamentals/Variable Examples C++

Overview

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

Data Types

 // 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

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

Discussion

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

 // 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

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

Discussion

Each new code element represents:

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

Temperature

 // 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

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

Discussion

Each new code element represents:

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

References

Wikiversity: Computer Programming

Programming Fundamentals