Children are taught the four functions of a calculator: addition, subtraction, multiplication and division, at an early age. Sometime after that, they are taught the percentage key and square root. But most school students advance to graphing and scientific calculators without ever learning the functions of an adding machine or business calculator. Unless one takes business classes in high school or college, the nondescript COST, SELL, MARGIN or 5/4 buttons make little sense. Whether the adding machine is made by Casio, Sharp, or an office supply retailer, the functions are similar.

### Function

All adding machines complete the basic functions of addition, subtraction, multiplication and division. The addition and subtraction functions work in continuous computation. Say you wanted to compute 1+1+2-1. On a regular four-function calculator, you would press keys in this sequence: 1, +, 1, +, 2, =. This would give you the total of 4. Then, you would press the minus key, the one key and the equal sign to get the answer of 3. On an adding machine, you would enter the following sequence: 1, +, 1, +, 2, +, 1, -. Where on a regular calculator the function precedes the number, the adding machine places the number before the function. Multiplication and division operates the same as a standard calculator.

### Function

The equal sign on a adding machine functions only when calculating multiplication or division functions. When totaling numbers with addition and subtraction, the diamond and asterisk keys provide answers. The diamond key prints a subtotal of the numbers tabulated to that point. The machine remembers the current total and allows the user to continue computing. The asterisk button completes the calculation, prints the total on the adding tape and ends the computation.

### Function

On every adding machine there are two switches. The first switch slides and locks in front of a 0, 1, 2, 3, or F. These numbers correspond to the number of decimal places to be displayed. When the switch is at zero, the computation rounds the solution to an equation to a whole number. The 1, 2 and 3 relate to the number of decimal places that will be displayed and rounded to. When in front of the F key, or full key, the adding machine will display all decimal places that will fit on the screen.

### Function

Related to the decimal place switch, is the rounding switch. This is denoted with a 5/4 and plus and minus symbols. When the switch is locked to 5/4, then the machine will not round any places. When switched to the plus, the machine will round up every equation with the last decimal place greater than or equal to five. Likewise, any decimal less than five will be rounded down.

### Function

Most business calculators carry tax calculation functions. There are usually two keys: TAX + and TAX -. Tax plus is a tax included total that calculates a number that reflects the sales tax rate. TAX - reflects a total that is pre-tax.

### Function

The COST, SELL and MARGIN keys assist sales professionals determine the markup margins of products. For example, a company sells widgets for $6 but they only cost $1 to make. To determine the margin of the widget, type the following sequence: 1, COST, 6, SELL, MARGIN. The answer displayed will be expressed as a percentage.