Adding calculators function somewhat differently from the typical mathematical or scientific calculators most people have experience using. Because an adding calculator (also known as an adding machine) accepts the mathematical function after the numbers have been input (as opposed to before the numbers as in a typical hand-held calculator), using one does require a somewhat different approach to the function being calculated.

Rather than interjecting the mathematical function between the two numbers being added together, as a scientific calculator does, an adding calculator accepts the mathematical function after each number is entered. The most basic example of this operation is in addition, where one number is entered, the plus sign (+) is pressed, then another number is entered and the plus sign (+) is pressed again. To start an addition function, enter the first addend (the first number to be added) and then press the plus (+) sign.

Add another addend. When the first addend is displayed, enter another addend (the number you wish to add) and press the plus (+) sign again. The sum of these two numbers will be displayed.

Repeat as necessary. You may continue to add as many numbers as necessary by repeating this process; simply enter the number you wish to add followed by the plus (+) sign.

## Performing Basic Calculations on an Adding Calculator: Subtraction

Clear the machine for subtraction. Adding machines always start from zero, so before any number can first be subtracted the machine must be cleared out and the minuend (the original number from which the second number will be subtracted) must be added to zero. To arrive at the minuend, first clear the machine by pressing the clear (C) button.

Add the minuend. When the adding machine displays zero, add the minuend by entering the number followed by plus (+).

Subtract the subtrahend. Once the minuend is displayed on the adding machine, the subtrahend (the number being subtracted) can then be entered. After the subtrahend is entered, press the minus (-) key and the difference will be displayed.

Repeat as necessary. When the difference is displayed, additional subtractions may be made by entering another subtrahend followed by the minus (-) symbol. Addition, multiplication or division functions may also be performed from the difference displayed on the adding machine.

## Performing Basic Calculations on an Adding Calculator: Multiplication

Clear the machine for multiplication. Adding machines always start from zero, so before any number can be multiplied the machine must be cleared out and the multiplicand (the original number to be multiplied) must be added to zero. To arrive at the multiplicand, first clear the machine by pressing the clear (C) button.

Add the multiplicand. When the adding machine displays zero, add the multiplicand by entering the number followed by plus (+).

Input the second multiplier (factor) and multiply. Once the multiplicand is displayed on the adding machine, the multiplier (the number by which you wish to multiply the first multiplicand) can then be entered. After the multiplier is entered, press the asterisk (*) key and the product will be displayed.

Repeat as necessary. When the product is displayed, additional multiplications may be made by entering another factor followed by the asterisk (*) symbol. Addition, subtraction or division functions may also be performed from the product displayed on the adding machine.

## Performing Basic Calculations on an Adding Calculator: Division

Clear the machine for division. Adding machines always start from zero, so before any number can be divided the machine must be cleared out and the dividend (the original number that will be divided by the second number) must be added to zero. To arrive at the dividend, first clear the machine by pressing the clear (C) button.

Add the dividend. When the adding machine displays zero, add the dividend by entering the number followed by plus (+).

Input the second multiplier (divisor) and divide. Once the dividend is displayed on the adding machine, the divisor (the number you wish to divide into the dividend) can then be entered. After the divisor is entered, press the obelus (division symbol) key and the result will be displayed.

Repeat as necessary. When the product is displayed, additional divisions may be made by entering another divisor followed by the obelus (division symbol). Addition, subtraction or multiplications functions may also be performed from the result displayed on the adding machine.