Logical Expressions

This section describes logical expressions - expressions resulting a Boolean value with comparison operations and logical operations.

Logical expression is a way of expressing a logical condition, upon which certain parts of the program execution flow can be altered. For example, a furniture store wants the following delivery charges in its invoice program: if the total amount of an order is less than \$200.00, delivery is charged as \$25.00; if the amount is greater than or equal to \$200.00, delivery is free. Here "amount is less than \$200.00" is a logical condition that needs to be entered in C# program as a logical express.

The most simplest logical conditions involves relational operators:

• ">": Greater than
• "<": Less than
• ">=": Greater than or equal
• "<=": Less than or equal
• "==": Equal
• "!=": Not equal

A relational operation can be entered into C# programs as a logical expression with the following syntax:

```logical_expression:
arithmetic_expression relational_operator arithmetic_express
```
After evaluation, a logical expression will produce a boolean value, true or false.

Examples of logical expressions are:

• "1 < 2": This is a simple logical expression. The resulting value is true.
• "1 > 2": This is also a simple logical expression. The resulting value is false.
• "quantity * price < 200.00": The arithmetic expression "quantity * price" will be evaluated first. Its result will be then compared with 200.00. The resulting value is true or false, depending on the resulting value of arithmetic expression.
• "exam_score == 100": If the value in exam_score is equal to 100, the resulting value will be true. Otherwise, it will be false.

Last update: 2010.