Referring to an action that takes place only if a specific condition is met. Conditional
expressions are one of the most important components of
programming languages because they enable a
program to act differently each time it is
executed, depending on the
input. Most programming languages use the word
if for conditional expressions. For example, the conditional
statement:
if x equals 1 exit
directs the program to exit if the variable x is equal to 1.
