An if statement is a selection statement that allows more than one possible flow of control. You can optionally specify an else clause on the if statement. If the test expression evaluates to false (or in C, a zero value) and an else clause exists, the statement associated with the else clause runs. If the test expression evaluates to true, the statement following the expression runs and the else clause is ignored. When if statements are nested and else clauses are present, a given else is associated with the closest preceding if statement within the same block.