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Programming Fundamentals/Variable Examples C++
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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