### DIGITAL SYSTEMS CALCULATORS

Click on the inputs or a row on the truth table to change the addends or the input carry.

## INFORMATION

A full-adder adds three bits and produces the sum and the carry as outputs. Two of these bits represent the current place values of the added numbers, while the third bit represents the carry from the previous digit.

The truth table of a full-adder is as follows:

In this table,

• x and y represent the addends,
• z represents the carry from the previous digit,
• S represents the sum and
• C represents the carry to the next digit.

The carry occurs only when at least two of the inputs are equal to logic-1. The sum is equal to 1 when only one or all of the addends are 1, otherwise it is 0.

Two possible circuit implementations of a full adder circuit are illustrated above. One of these implementations uses the classical logic gates and the the other uses two half-adders.

### WHAT IS FULL-ADDER LEARNING TOOL?

• Allows the user to select the input values and
• Illustrates the outputs on the circuits and the truth table.

### HOW TO USE THE FULL-ADDER LEARNING TOOL?

You can select the input values yourself or set them randomly.

• #### USER INPUTS

To toggle the input values between 1 and 0, click on the inputs of circuits or the block diagram.

Or click on any row on the truth table to set the input values.

• #### RANDOM INPUTS

The DIE ICON generates a random set of values for the inputs.