Tag: logic gates

Logic Gates Programming Assignment

To follow up on the introduction to Logic Gates post, this assignment is intended to help students practice using functions and logic statements.

  1. Write a set of function that act as logic gates. That is, they take in one or two inputs, and gives a single true or false output based on the truth tables. Write functions for all 8 logic gates in the link. An example python program with a function for an AND gate (the function is named myAND) is given in the glowscript link below.
  2. Write a function that uses these functions to simulate an half-adder circuit. Create a truth table for the input and output.
  3. Write a function that uses the gate functions to simulate a full-adder circuit. Create a truth table for the input and output.

Here’s a program with an example function for an AND gate (called myAND), and a simple program to test it.

The half-adder circuit is shown below.

Half Adder circuit.

The full adder circuit:

Full adder circuit by en:User:Cburnett on wikimedia.org

Logic Gates

Truth tables by Seth Abels.

Logic gates are the building blocks of computers. The gates in the figure above take one or two inputs (A and B) and give different results based on the type of gate. Note that the last row of gates are just the opposite of the gates in the row above (NAND gives the opposite output to AND).

As an example, two gates, an AND and an XOR, can be used to make a half-adder circuit

Half adder circuit

By feeding in the four different combinations of inputs for A and B ([0, 0], [1, 0], [0, 1], and [1, 1]) you can see how these two gates add the two numbers in binary.

Creating a truth table for the half adder.

I find this to be an excellent introduction to how computers work and why they’re in binary.