How are Binary Codes Used?

Date: 01/25/2001 at 10:27:10
From: Leoni Bisset
Subject: (Use of) binary codes

I'm working on a project about binary codes. I've figured out how the 
binary system works and how to 'translate' from binary to decimal 
codes. The main problem is actually the USE of the binary code. 
I have to explain how it is used in computers, and I only know that 
the computer can only read 0 and 1. I also have to look for other 
uses, like a light, morse code, braille, bar codes, etc. and explain 
how they work. My teacher told me to ask in a shop how their bar code 
system works, but I haven't had time yet. I've also asked others for 
help, but they couldn't help me. 

What I would like to find out is:

- How a computer works, exactly (precise, but not too much info);
- Perhaps some other usages of the binary system and how they work.

Some tips or good sites would really help me on my way.

Thank you very much in advance,
Yours sincerely,
Leoni Bisset

Date: 01/25/2001 at 12:05:46
From: Doctor TWE
Subject: Re: (Use of) binary codes

Hi Leoni - thanks for writing to Dr. Math.

A "binary code" is any system that uses only two states (0 or 1, on or 
off, true or false, etc.) The base 2, or binary, number system is just 
one example, as you mentioned. Let me comment some of the other 
examples you gave.

With light, I assume you (or your teacher) means lighting systems. The 
light itself isn't binary, but the switching systems - ranging from a 
simple on/off wall switch to a two-way switch for complex stage 
lighting systems - are often binary. These can be represented with 
digital logic gates and operations.

Morse code was the first binary code used in telecommunications. 
Though W. F. Cooke and Charles Wheatstone had developed the electric 
telegraph earlier in England (in 1830), it was Morse's code that 
popularized the use of the device. Morse code - unlike most computer 
codes in use today - was a variable-length code, i.e. different 
characters had different numbers of "bits" (dots and dashes).

Braille is an alphabet for the blind that uses a series of raised 
bumps that can be detected by the trained finger. Each dot position 
can either be raised or not raised - hence it is a binary code.

As to bar codes - I'm not so sure that someone at a shop that uses 
them necessarily knows how they work. You might be better off reading 
about them on the Web or in an encyclopedia.

Here are some other binary codes used in computers and other 
electronic devices - that is the field in which binary codes are used 
the most. After all, every "digital" device - from CDs to digital 
televisions to telephones to calculators and computers - uses some 
form of binary code. You can find more information on these codes by 
typing their names into a good Web search engine, or looking in a 
relatively recent encyclopedia (or reference book on digital 
electronics).

     Binary Coded Decimal (BCD) - popular in calculators
     2'421 BCD - alternative BCD code
     Excess-3 code - another alternative BCD code
     Gray code - used with many optical sensors (incl. some bar codes)
     ASCII - used by computers to represent text
     Baudot - text code used by teletypes in the 50's and 60's
     EBCDIC - an IBM alternatice to ASCII
     MIDI code - used for electronic music
     RLL codes - used in storage devices like disk drives
     MP3 - an audio file format
     JPEG, MPEG - picture & video file formats

Here are some related topics. These are not binary codes themselves, 
but may help you to understand some of the uses and applications of 
binary codes.

     Boolean algebra, symbolic logic, propositional calculus -
        these are all variations of the same concepts.
     Error detecting and correcting schemes - Like parity, checksum, 
        CRC and Reed-Solomon code
     Venn diagrams and Karnaugh mapping

I hope this helps. If you have any more questions, write back.

- Doctor TWE, The Math Forum
  http://mathforum.org/dr.math/