- Use common symbols for: + Addition, - Subtraction, * Multiplication, / Division, ^ exponent operator.

- Follow the standard order of operations taught in Algebra courses: Parentheses, Exponents, Multiplication and Division, Addition and Subtraction.

- Follow conventions for x and y variable definitions, for example, in the equation for a line:

    y=mx + b

    x represents the independent variable plotted on the horizontal axis/abscissa, and

    y is the dependent variable plotted on the vertical axis/ordinate.

- Use of upper/lower case in expressions is arbitrary.

- Use of "y=" at the beginning of the expression is optional.

- Use of the * for multiplication is optional, for example, y=5*x+7 can be entered as y=5x+7.

- Ability to just put in the operator and the new value.
    so entering:
    251+139 would give 390, but then just entering:
    +85.68 would give 475.68 (i.e., 390+85.68)

 

- Trigonometric functions use radians (instead of degrees).  Multiply degrees by pi/180 to convert to radians.