Order of operations
This means that if, in a mathematical expression, a subexpression appears between two operators, the operator that is higher in the above list should be applied first.
The "Addition/Subtraction" in the mnemonics should be interpreted as that any additions and subtractions should be performed in order from left to right. Similarly, the expression a ÷ b × c might be read multiple ways, but the "Multiplication/Division" in the mnemnonic means the multiplications and divisions should be performed from left to right.
while more sophisticated calculators will use a more standard priority, for example typing
Chain input expects two operands and an operator. When the next operator is pressed, the expression is immediately evaluated and the answer becomes the left hand of the next operator. Advanced calculators allow entry of the whole expression, grouped as necessary, and evaluates only when the user uses the equals sign.
When the user is unsure how a calculator will interpret an expression, parentheses can be used to remove the ambiguity.
Examples: (Note: in the examples below, '≡' is used to mean "is identical to", and not to be interpreted as an actual assignment operator used as part of the example expression.)