A Boolean expression is an expression that results in a Boolean value, that is, either `true`

or `false`

.

A simple Boolean expression is written as

*Operand1 **Comparison Operator** Operand2*

where

and*Operand1**Operand2*

can be one of those shown in the next table*Comparison Operator*

## PHP

PHP Comparison Operator |
Description |

== | Equal (not assignment) |

!= | Not equal |

> | Greater than |

< | Less than |

>= | Greater than or equal to |

<= | Less than or equal to |

Notice: A very common mistake that novice programmers make when writing PHP programs is to confuse the assignment operator with the equal operator. They frequently make the mistake of writing`$x = 5`

when they actually want to say`$x == 5`

.

Here are some examples of Boolean expressions in PHP:

`$x == 5`

. This can be read as “*test if*`$x`

*is equal to 5*”`$x > $y`

. This can be read as “*test if*`$x`

*is greater than*`$y`

”`$x <= $y`

. This can be read as “*test if*`$x`

*is less than or equal to*`$y`

”`$x != 3 * $y + 4`

. This can be read as “*test if*`$x`

*is not equal to the result of the expression*`3 * $y + 4`

”`$s == "Hello"`

. This can be read as “test if`$s`

is equal to the word ‘Hello’”

Notice: For humans, Boolean expressions should be interpreted as questions. They should be read as “Is something equal to/greater than/less than something else?” and the answer is just a “Yes” or a “No” (`true`

or`false`

).

Moreover, given that a Boolean expression actually returns a value (`true `

or `false`

), this value can be directly assigned to a variable. For example, the expression

`$a = $x > $y;`

assigns a value of `true `

or `false`

to variable` $a`

. It can be read as “*If the content of variable **$x** is greater than the content of variable **$y**, assign the value **true** to variable **$a**; otherwise, assign the value **false**.*” This next example displays the number 1 on the screen.

<?php $x = 8; $y = 5; $a = $x > $y; echo $a; ?>

Notice: Please note that in PHP, the Boolean value true can also be represented by the value of 1.

## Java

Java Comparison Operator |
Description |

== | Equal (not assignment) |

!= | Not equal |

> | Greater than |

< | Less than |

>= | Greater than or equal to |

<= | Less than or equal to |

Notice: A very common mistake that novice programmers make when writing Java programs is to confuse the assignment operator with the equal operator. They frequently make the mistake of writing`x = 5`

when they actually want to say`x == 5`

.

Remember: In Java, in order to test if two strings are lexicographically equal, you need to use the`equals()`

method. For example, the statement`a.equals(b)`

tests if the content of the string variable`a`

is equal to the content of string variable`b`

.

Remember: In Java, in order to test if one string is lexicographically “greater” or “less” than another string, you need to use the`compareTo()`

method. For example, the statement`a.compareTo(b)`

compares the content of the string variable`a`

to the content of string variable`b`

and returns a value greater than 0 if variable`a`

is lexicographically greater than variable`b`

, or a value less than 0 if variable`a`

is lexicographically less than variable`b`

.

Here are some examples of Boolean expressions in Java:

`x == 5`

. This can be read as “*test if*`x`

*is equal to 5*”`x > y`

. This can be read as “*test if*`x`

*is greater than*`y`

”`x <= y`

. This can be read as “*test if*`x`

*is less than or equal to*`y`

”`x != 3 * y + 4`

. This can be read as “*test if*`x`

*is not equal to the result of the expression*`3 * y + 4`

”`s.equals("Hello") == true`

. This can be read as*“test if*`s`

*is equal to the word ‘Hello’”*

Notice: For humans, Boolean expressions should be interpreted as questions. They should be read as “Is something equal to/greater than/less than something else?” and the answer is just a “Yes” or a “No” (`true`

or`false`

).

Moreover, given that a Boolean expression actually returns a value (`true `

or `false`

), this value can be directly assigned to a variable. For example, the expression

`a = x > y;`

assigns a value of `true `

or `false`

to variable` a`

. It can be read as “*If the content of variable **x** is greater than the content of variable **y**, assign the value **true** to variable **a**; otherwise, assign the value **false**.*” This next example displays the number` true`

on the screen.

public static void main(String[] args) throws java.io.IOException { int x, y; boolean a; x = 8; y = 5; a = x > y; System.out.println(a); }

## C++

C++ Comparison Operator |
Description |

== | Equal (not assignment) |

!= | Not equal |

> | Greater than |

< | Less than |

>= | Greater than or equal to |

<= | Less than or equal to |

Notice: A very common mistake that novice programmers make when writing C++ programs is to confuse the assignment operator with the equal operator. They frequently make the mistake of writing`x = 5`

when they actually want to say`x == 5`

.

Here are some examples of Boolean expressions in C++:

`x == 5`

. This can be read as “*test if*`x`

*is equal to 5*”`x > y`

. This can be read as “*test if*`x`

*is greater than*`y`

”`x <= y`

. This can be read as “*test if*`x`

*is less than or equal to*`y`

”`x != 3 * y + 4`

. This can be read as “*test if*`x`

*is not equal to the result of the expression*`3 * y + 4`

”`s == "Hello"`

. This can be read as*“test if*`s`

*is equal to the word ‘Hello’”*

Notice: For humans, Boolean expressions should be interpreted as questions. They should be read as “Is something equal to/greater than/less than something else?” and the answer is just a “Yes” or a “No” (`true`

or`false`

).

Moreover, given that a Boolean expression actually returns a value (`true `

or `false`

), this value can be directly assigned to a variable. For example, the expression

`a = x > y;`

assigns a value of `true `

or `false`

to variable` a`

. It can be read as “*If the content of variable **x** is greater than the content of variable **y**, assign the value **true** to variable **a**; otherwise, assign the value **false**.*” This next example displays the number` true`

on the screen.

#include <iostream> using namespace std; int main() { int x, y; bool a; x = 8; y = 5; a = x > y; cout << a; return 0; }

## C#

C# Comparison Operator |
Description |

== | Equal (not assignment) |

!= | Not equal |

> | Greater than |

< | Less than |

>= | Greater than or equal to |

<= | Less than or equal to |

Notice: A very common mistake that novice programmers make when writing C# programs is to confuse the assignment operator with the equal operator. They frequently make the mistake of writing`x = 5`

when they actually want to say`x == 5`

.

Remember: In C#, in order to test if one string is lexicographically “greater” or “less” than another string, you need to use the`CompareTo() method`

. For example, the statement`a.CompareTo(b)`

compares the content of the string variable`a`

to the content of string variable`b`

and returns a value greater than 0 if variable`a`

is lexicographically greater than variable`b`

, or a value less than 0 if variable`a`

is lexicographically less than variable`b`

.

Here are some examples of Boolean expressions in C#:

`x == 5`

. This can be read as “*test if*`x`

*is equal to 5*”`x > y`

. This can be read as “*test if*`x`

*is greater than*`y`

”`x <= y`

. This can be read as “*test if*`x`

*is less than or equal to*`y`

”`x != 3 * y + 4`

. This can be read as “*test if*`x`

*is not equal to the result of the expression*`3 * y + 4`

”`s == "Hello"`

. This can be read as*“test if*`s`

*is equal to the word ‘Hello’”*

Notice: For humans, Boolean expressions should be interpreted as questions. They should be read as “Is something equal to/greater than/less than something else?” and the answer is just a “Yes” or a “No” (`true`

or`false`

).

`true `

or `false`

), this value can be directly assigned to a variable. For example, the expression

`a = x > y;`

assigns a value of `true `

or `false`

to variable` a`

. It can be read as “*If the content of variable **x** is greater than the content of variable **y**, assign the value **true** to variable **a**; otherwise, assign the value **false**.*” This next example displays the number` true`

on the screen.

static void Main() { int x, y; bool a; x = 8; y = 5; a = x > y; Console.Write(a); Console.ReadKey(); }

## Visual Basic

VB Comparison Operator |
Description |

= | Equal |

<> | Not equal |

> | Greater than |

< | Less than |

>= | Greater than or equal to |

<= | Less than or equal to |

Remember: In Visual Basic, in order to test if one string is lexicographically “greater” or “less” than another string, you need to use the`CompareTo()`

procedure. For example, the statement`a.CompareTo(b)`

compares the content of the string variable`a`

to the content of string variable`b`

and returns a value greater than 0 if variable`a`

is lexicographically greater than variable`b`

, or a value less than 0 if variable`a`

is lexicographically less than variable`b`

.

Here are some examples of Boolean expressions in Visual Basic:

`x = 5`

. This can be read as “*test if*`x`

*is equal to 5*”`x > y`

. This can be read as “*test if*`x`

*is greater than*`y`

”`x <= y`

. This can be read as “*test if*`x`

*is less than or equal to*`y`

”`x <> 3 * y + 4`

. This can be read as “*test if*`x`

*is not equal to the result of the expression*`3 * y + 4`

”`s = "Hello"`

. This can be read as*“test if*`s`

*is equal to the word ‘Hello’”*

Notice: For humans, Boolean expressions should be interpreted as questions. They should be read as “Is something equal to/greater than/less than something else?” and the answer is just a “Yes” or a “No” (`true`

or`false`

).

`true `

or `false`

), this value can be directly assigned to a variable. For example, the expression

`a = x > y`

`true `

or `false`

to variable` a`

. It can be read as “*If the content of variable **x** is greater than the content of variable **y**, assign the value **true** to variable **a**; otherwise, assign the value **false**.*” This next example displays the number` true`

on the screen.

Sub Main() Dim x, y As Integer Dim a As Boolean x = 8 y = 5 a = x > y Console.Write(a) Console.ReadKey() End Sub

## Python

Python Comparison Operator |
Description |

== | Equal (not assignment) |

!= | Not equal |

> | Greater than |

< | Less than |

>= | Greater than or equal to |

<= | Less than or equal to |

Notice: A very common mistake that novice programmers make when writing Python programs is to confuse the assignment operator with the equal operator. They frequently make the mistake of writing`x = 5`

when they actually want to say`x == 5`

.

Here are some examples of Boolean expressions in Python:

`x == 5`

. This can be read as “*test if*`x`

*is equal to 5*”`x > y`

. This can be read as “*test if*`x`

*is greater than*`y`

”`x <= y`

. This can be read as “*test if*`x`

*is less than or equal to*`y`

”`x != 3 * y + 4`

. This can be read as “*test if*`x`

*is not equal to the result of the expression*`3 * y + 4`

”`s = "Hello"`

. This can be read as*“test if*`s`

*is equal to the word ‘Hello’”*

Notice: For humans, Boolean expressions should be interpreted as questions. They should be read as “Is something equal to/greater than/less than something else?” and the answer is just a “Yes” or a “No” (`true`

or`false`

).

`true `

or `false`

), this value can be directly assigned to a variable. For example, the expression

`a = x > y`

`true `

or `false`

to variable` a`

. It can be read as “*If the content of variable **x** is greater than the content of variable **y**, assign the value **true** to variable **a**; otherwise, assign the value **false**.*” This next example displays the number` true`

on the screen.

x = 8 y = 5 a = x > y print(a)

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