Binary Data Storage and Manipulation
Demonstrating Physical Representation and Implementation
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For the practical portion of our project, we have decided to build an 8-bit binary adder out of simple circuitry. This device takes two 8-bit binary numbers as input and outputs their sum, in binary. This device represents the core technology of the Arithmetic Logic Unit (ALU) of a modern CPU, which is the circuitry used to perform mathematical operations such as addition and subtraction on numbers in memory. While our project is not quite as feature packed as a modern ALU, it does demonstrate the concept by performing addition and providing some information about the answer in form of carry, overflow, zero and sign flags, all parts of a standard ALU. The carry flag indicates if the answer is too large for the word-size, in our case 8-bits. The overflow flag indicates if the sum has the wrong sign considering the input. The zero flag simply indicates if the answer is zero. The sign flag simply indicates if the most significant bit (MSB), or the bulb on the far left of the answer, is one -- this is called the sign flag because computers represent negative numbers in a format called two's complement which is always charactereized by a 1 for the MSB. Our device takes input from two arrays of switches, allowing human input of the 2 binary numbers (bit-patterns) to be added. The input from the switches is fed into the circuitry which then computes and outputs the answer to an array of relays which activate standard sized incandescent colored light bulbs to display the bit pattern of the sum as well as the flags discussed above.  Alternatively, our device can take input and send output in parallel via a standard IDE ribbon cable. There is a pin-header on the circuit board which would allow for this to happen. This allows our device to be used by another circuitry project which requires the ability to add numbers. An example of such a device that might make a good project is circuitry that converts the binary output of our project to a decimal answer. |