CSC 101: Lab #5 Prelab Boolean Logic Practice Due Date: 5:00pm, day after lab session

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1 Name: Username: Lab Date and Time: CSC 101: Lab #5 Prelab Boolean Logic Practice Due Date: 5:00pm, day after lab session Purpose: The purpose of this pre-lab is to provide you with hands-on experience in manipulating and designing Boolean logic circuits using a logic gate simulator. There are a set of questions on pages 5 and 6 of this document that you should answer and submit at the beginning of lab. Background reading : Read pages of your textbook (Brookshear, Computer Science: An Overview) and, review the lecture section Powerpoint notes from Wednesday, 2/9, Friday, 2/11, and Monday, 2/14. Software check: Make sure you can access the following website: The software at that website will allow us to design and test various logic circuits. Hit Cancel on the small window that pops up when you first load the page. You should see a website load that looks like the following: The simulator interface provides a toolbox of logic gates on the left-hand side of the screen and a desktop interface on the right-hand side of the screen. The desktop area is where the gates in the toolbox can be dragged and connected together. At this time, please watch the short (3 minutes) video linked on the next page. This video discusses using a similar tool, LogicGateSimulator. While watching a video about another piece of software might seem odd, that tool is very similar to the logic.ly software we will be using in lab, and the video provides a great overview of how to go about designing gates in such a tool. Don t worry about the circuits the demo shows being built -- instead focus on the processes being used dragging and dropping gates, creating wires (links) between gates, and turning inputs on and off. Video to watch: The differences you will see when working with our tool, logic.ly, instead of LogicGateSimulator are that in our tool, the inputs are light-switches, and the outputs are light bulbs.

2 Note that in these tools the inputs of each logic gate are on the left-hand side, and the outputs are on the right-hand side. After watching the video, review the information about the key logical gates listed in the table below. The explanation of the NOT, AND, OR, and XOR gates should match what you saw in lecture already. Useful Boolean logic gates: Name Symbol Truth Table NOT (Negation) Input Output 0 (False) 1 (True) 1 (True) 0 (False) AND OR XOR (Exclusive OR) INPUT Note the subtle variation from OR. Value 0 (False): Input Input Output A B 0 (F) 0 (F) 0 (F) 0 (F) 1 (T) 0 (F) 1 (T) 0 (F) 0 (F) 1 (T) 1 (T) 1 (T) Input Input Output A B 0 (F) 0 (F) 0 (F) 0 (F) 1 (T) 1 (T) 1 (T) 0 (F) 1 (T) 1 (T) 1 (T) 1 (T) Input Input Output A B 0 (F) 0 (F) 0 (F) 0 (F) 1 (T) 1 (T) 1 (T) 0 (F) 1 (T) 1 (T) 1 (T) 0 (F) Value 1 (True): (switch is up ) (switch is down and blue )

3 OUTPUT Value 0 (False): Value 1 (True): (bulb is white) (bulb is blue) Practice with interface: To help learn more about this tool we will be making use of, let s use it to verify the actions of the OR gate. Read below how I made use of logic.ly to do this. You don t have to build a circuit at the moment; just read along! I need to drag an OR gate onto the desktop. Then I drag two Switches onto the desktop and connect them to the lefthand (input) side of the OR gate. Note that I can drag Labels next to the switches and outputs to help me remember their purpose later on. I will label the top input A, the bottom input B, and, in a little bit, the output X. In the rest of the lab, the inputs will be labeled in this {A, B, } order (top to bottom). Finally, I can add a Light Bulb output, connecting it to the right hand of the OR gate and labeling it X. Now, to test this gate setup. Initially, I will find (as shown in the picture above) the input switches are up and white, indicating that they have the value 0. The output light bulb is also white, indicating it has a 0 value. This is reasonable, as evaluating 0 OR 0 (false OR false) should return the value 0 (false).

4 I will now try each of the other three combinations of inputs: 1 OR 0, 0 OR 1, and 1 OR 1. To turn an input on or off, I just need to click on the appropriate switch and it will change color. White and Up indicates 0 (off/false) and Blue and Down indicates 1 (on/true) 1 (True) OR 0 (False) output of 0 (True) 0 (False) OR 1(True) output of 1 (True) 1(True) OR 1(True) output of 1 (True) From the pictures above, it appears my OR circuit is correct! At this point, you should try to gain experience in working with the logic.ly interface by experimenting. Some suggestions for experimenting are: o Drag gates, inputs, and outputs onto the desktop and connect them maybe try to rebuild the OR gate setup I created above. o Practice dragging between the connector hooks on inputs, outputs, and gates to make connections. o Click on a wire connection to remove the connection. o Practice flipping switches on and off and monitoring outputs.

5 Name: Username: Lab Date and Time: Pre Lab #5 Questions: Answer the following questions, using this pre-lab document as a reference. These questions are worth 20 of your total 100 points for the lab. Submit your answers at the beginning of your lab section on Tuesday. 1. [8 pts (4,4)] One of the circuits we will build in lab is called a NAND circuit. This is an AND gate with two Switch inputs. The difference that separates a NAND circuit from an AND circuit is that the AND gate output is negated (sent through a NOT gate), with the NOT gate s output then being sent to a LightBulb output. a. Sketch, by hand (not in the logic.ly tool), a picture of a complete NAND circuit by using two Switch inputs, an AND gate, a NOT gate, and a LightBulb output connected in the manner described above. b. Given the table below, fill in the expected correct values for the output of the NAND gate. Do not use the logic.ly tool to do this instead do it by hand using the tables on page 2. Input A (Top Input) Input B (Bottom Input) AND Gate Output (do this first!) Negation Of AND Gate Output (NAND) 2. [12 pts (4, 4, 4)] Below is an image of a circuit I have designed in logic.ly. [This is the corrected, intended image (with a NOT gate) as indicated in the Monday midnight ]

6 a. Indicate the number and type of different components in the circuit above 1. There are (number) of (type of component) 2. There are (number) of (type of component) 3. There are (number) of (type of component) 4. There are (number) of (type of component) b. Write the equivalent Boolean expression and the complete truth table for the circuit above. [There is a similar problem to this on the homework!] Equivalent Boolean expression: Truth Table: A B Use this column for intermediate work if desired Output Value X Remember to review the Lab 4 material in preparation for the Lab 4 quiz. The quiz questions are focused on processes and activities employed during the previous lab session.