Boolean Expressions

Branching and looping structures evaluate the logic to execute a branch or execute a loop. That logic could test a certain value, could be a comparison of values, or could test a logical relationship, and it can be written as an expression. The expression is evaluated as a Boolean value; that is, true or false by the branching and looping structures. For branching, the expression serves as an entry check for that branch so that we can decide whether to choose that branch of code or not. For looping, the expression might serve as an entry or exit check for that loop so that we can decide how many times the loop should iterate. For example, to email a list of persons, we can write an expression to determine the size of the list so that we set how many times we do the emailing task and write another expression that checks the email address validity to send the email.

A Boolean expression is an expression that produces a result of either true or false. A Boolean...