Infix notationInfix notation is the arithmetic formula notation known to most people, in which operators are written between the operands they act on. It is not as simple to parse by computer as postfix notation, but many programming languages use it to take advantage of its familiarity.
In infix notation, unlike in postfix or prefix notations, parentheses surrounding groups of operands and operators are necessary to indicate the intended order in which operations are to be performed. In the absense of parentheses, certain precedence rules determine the order of operations. These are explained in the order of operations article.