# Alphanumeric Representation

## Encoding Alphanumerics with the ASCII Table

This ASCII (American Standard Code for Information Interchange) table outlines a common set of conventions established for converting between binary values and alphanumeric characters.

The table functions as a mapping from binary values to alphanumeric symbols. This is an arbitrary mapping that was constructed many years ago. Note that there is no inherent meaning that dictates that the double-quote character, `"`, should map to `00100010` (or `34` in decimal notation). Much like your groups are doing for your controller projects, this table and its mappings were defined by real people.

Watch this tutorial for a demonstration of how this table is read:

You can convert alphanumerics into binary (or vice versa) using the ASCII table as the tutorial explains, or you can use one of the many free transducers found online, like this Binary to Text Converter. Try it out!

Note about “computational thinking": Remember, one aspect of computational thinking is abstraction. Computers can’t understand language or symbols like we do, but they can do mathematical computations really quickly. The abstraction that maps values to symbols creates the illusion that computers work directly with language constructs.

## Errors/Noise

Have you considered the fact that `g` and `w` are only different by one bit?

`g` is encoded as `01100111`
`w` is encoded as `01110111`

If somehow this bit were “flipped,” a confusing message may result:

This cake is really wood. Try some!
Umm, no thanks? I’m not a termite.

Computer scientists call problems such as these noise. Noise is irrelevant or meaningless data that has found its way into otherwise meaningful code. Noise can make it difficult for computers to efficiently and effectively represent binary as alphanumeric or other representations (e.g., images, audio). Luckily, algorithms have been developed to detect and even correct such problems, which is why they don’t typically occur.

Otherwise, as a result of noise, instead of what you expect, you might end up missing a really delicious piece of cake, or wind up with a blue screen or the spinning wheel of death.

"There’s always the hope that if you sit and watch for long enough, the beachball will vanish and the thing it interrupted will return.”— The Eternal Flame, xkcd #961 (Randal Munroe)