• When several operations occur in an expression, each part is evaluated and resolved in a predetermined order is called operator precedence.
  • In mathematics and computer programming, the order of precedence is used to perform first in order to evaluate a given mathematical expressions.
  • Some of the mnemonics like BODMAS, PEDMAS, BEDMAS, BIDMAS are used in different countries like UK, India, Australia, US. These are often used to help students remember the rules, involving the first letters of words representing various operations.
      For example,
  • Calculators are also used these operator precedence rules, input expects two operands and an operator. 
  • When the next operator is pressed, the expression is immediately evaluated and answer becomes the left hand of the next operator. Advanced calculators allow the entry of whole expression , grouped as necessary, and evaluates only when the user  uses the equal sign.
        For example, 
  • Some programming languages use precedence rule that conform to the order commonly used in mathematics, others such as APL, Smalltalk have no precedence rules.
  • Precedence Rules:
        

  • For example,