Computers use codes to represent information. The basic unit of information is the bit, which stands for binary digit, and could be either a 0 or a 1. The Information unit begins with examples of one-bit messages, such as a knock on the door. To add information, you can knock softly or loudly; once or repeatedly.. Computers handle information in digital form, which has discrete possibilities, but there are other devices that use analog information, which can vary continuously. Light switches are digital, while dimmers are analog. Students look at a variety of devices, and sort them according to whether they handle information in analog or digital form. To measure the amount of information, students play a guessing game to determine a secret number between 1 and 100. How many yes/no questions do you need? The instructor then plays the game against the class, and determines the number by getting the answers to seven questions or less. A number from 1 to 100 can be represented by a seven-bit binary number, and therefor contains seven bits of information. Other examples of information representation are seven- and fourteen-segment displays found on digital clocks and microwaves, and 35-bit 5 x 7 arrays found on street signs, store displays, trains and buses. Students learn how this works by playing the game of using counters or pennies to create numbers and letters on a 5 x 7 grid.