C# Booleans
C# Booleans
Very often, in programming, you will need a data type that can only have one of two values, like:
- YES / NO
- ON / OFF
- TRUE / FALSE
For this, C# has a bool
data type, which can take the values true
or false
.
Boolean Values
A boolean type is declared with the bool
keyword and can only take the values true
or false
:
Example
bool isCSharpFun = true;
bool isFishTasty = false;
Console.WriteLine(isCSharpFun); // Outputs True
Console.WriteLine(isFishTasty); // Outputs False
However, it is more common to return boolean values from boolean expressions, for conditional testing (see below).
Boolean Expression
A Boolean expression returns a boolean value: True
or False
, by comparing values/variables.
This is useful to build logic, and find answers.
For example, you can use a comparison operator, such as the greater than (>
) operator to find out if an expression (or a variable) is true:
Example
int x = 10;
int y = 9;
Console.WriteLine(x > y); // returns True, because 10 is higher than 9
Or even easier:
In the examples below, we use the equal to (==
) operator to evaluate an expression:
Example
int x = 10;
Console.WriteLine(x == 10); // returns True, because the value of x is equal to 10
Example
Console.WriteLine(10 == 15); // returns False, because 10 is not equal to 15
Real Life Example
Let's think of a "real life example" where we need to find out if a person is old enough to vote.
In the example below, we use the >=
comparison operator to find out if the age (25
) is greater than OR
equal to the voting age limit, which is set
to 18
:
Example
int myAge = 25;
int votingAge = 18;
Console.WriteLine(myAge >= votingAge);
Cool, right? An even better approach (since we are on a roll now), would be to wrap the code above in an
if...else
statement, so we can perform
different actions depending on the result:
Example
Output "Old enough to vote!" if myAge
is greater than or equal to 18
. Otherwise output "Not old enough to vote.":
int myAge = 25;
int votingAge = 18;
if (myAge >= votingAge)
{
Console.WriteLine("Old enough to vote!");
}
else
{
Console.WriteLine("Not old enough to vote.");
}
The boolean value of an expression is the basis for all C# comparisons and conditions.
You will learn more about conditions (if...else
) in the next chapter.