Symbols are images used to represent a bigger idea. Symbols are simple and standardized, which distinguishes them from other forms of images such as photographs or illustrations. In order for a symbol to work, people need to agree on its meaning. Can you think of some examples? (Show the following 4 examples before or after asking audience to share theirs.)

Codes and ciphers are often used interchangeably, though they are technically two different things. We will study both. A cipher is what we usually mean when we say code--it is a systems by which individual letters/characters are replaced with others by following an algorithm. Famous examples include the Caesar cipher, which substitutes the letters of the alphabet for each other by shifting the ciphertext down by four letters from the plaintext, so that A becomes D, and so on. On the other hand, a code using a symbol/word/phrase to stand for a different word or phrase. Codes require a codebook, which is essentially a dictionary that maps the codewords and their meanings.
For the next few images, determine if it's a code or cipher.

Cipher

Cipher

Code

Cipher

Code