Most programs make decisions based on the truth or falsity of some condition. If the condition is met, i.e:, the condition is true, some action is taken, or if the condition is not met, i.e.:, the condition is false, another action is taken.
Conditions can be formed by using the equality and relational operators summarized in the table below:
| C++ equality or relational operator |
Example of C++ condition |
Meaning of |
| == | x == y | x is equal to y |
| != | x != y | x is not equal to y |
| > | x > y | x is greater than y |
| < | x < y | x is less than y |
| >= | x >= y | x is greater than or equal to y |
| <= | x <= y | x is less than or equal to y |
The result of an equality or relational operator is either true (non-zero) or false (zero). The computer returns as a result of a comparison a true value or a false value which may then be tested using "control structures" which will be covered in the topics that follow.
The following program will display the results of each equality and relational operator using the cout object. A true result is normally any non-zero value while a false result will be displayed as zero:
Run the program below to see the results displayed.
#include <iostream.h>
main()
{
int x = 10;
int y = 5;
int z = 10;
// Show the results of the operators ...
cout << "x = " << x << endl;
cout << "y = " << y << endl;
cout << "z = " << z << endl << endl;
cout << "The TRUE expression ( x == z ) evaluates to " << ( x == z ) << endl;
cout << "The TRUE expression ( x != y ) evaluates to " << ( x != y ) << endl;
cout << "The TRUE expression ( x > y ) evaluates to " << ( x > y ) << endl;
cout << "The FALSE expression ( x < z ) evaluates to " << ( x < z ) << endl;
cout << "The TRUE expression ( x >= y ) evaluates to " << ( x >= y ) << endl;
cout << "The FALSE expression ( x <= y ) evaluates to " << ( x <= y ) << endl;
cout << "The TRUE expression ( y < x < z ) evaluates to " << ( y < x < z ) << endl;
return 0;
}