NWA-PCUG Newsletter Article
Bits, Bytes, OR Why Do We Get E-mail We Can't Read?
by John R. Clark - March 97
firstname.lastname@example.org (click to email author)
Have you ever gotten e-mail that you can't read because it appears to be just a collection of gibberish? What causes it. The answer lies in the growth of bits per byte in computers.
In the early days prior to 1965 most computer memory consisted of a collection of little ferrite donuts with 4 wires through each one. Building such a memory was labor intensive and expensive. In those days 8 Kbytes was considered big; now 8 Mbytes is small. The old IBM 1620 grouped 5 binary digits (bits) to form one character or byte. Five bits gave you 32 characters which was plenty for numbers but letters required 2 bytes for representation. Business machines like the IBM 1401 had a 6 bit byte or 64 characters. However this would not give you access to upper and lower case letters, the digits and all the punctuation you would like.
In the mid 1960s the US Bureau of Standards and most of the computers makers as well as those who made the peripheral components came up with a 7 bit byte giving 128 possible characters known as the ASCII code.
Unfortunately the big boy on the block IBM decided to use chip memory and an 8 bit byte on their new S/360 machines. Today some form of an 8 bit byte code is used on most all computers but the peripherals still tend to use the ASCII code.
This means that you may have a little difficulty sending your fancy MS Word document which has many embedded characters to Auntie Elm who only has a simple e-mail system. There are however three major ways of converting your many characters to just 64 which can be sent down a twisted pair telephone line to any system.The three systems are MIME Multipurpose Internet Mail Extension UUE A Unix system BINHEX An Apple Mac system
Using the fact that 64x64x64x64 = 256x256x256 all three systems with the aid of a little bit-twiddling, map three of the 8-bit characters into a 64 character collating system. The fly in the ointment is they don't use the same 64 characters hence most e-mail systems will not work with all three.
Below are the 64 character collating sequences that are used for encrypting e-mail to enable sending all 256 characters of the computer down a twisted pair.MIME ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-/ UUE `!"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_ BINHEX !"#$%&'()*+,-012345689@ABCDEFGHIJKLMNPQRSTUVXYZ[`abcdefhijklmpqr
The UUE and BINHEX have some identification text in the front which should be handled if you write your own decoding programs.
If any member of the NWAPCUG gets one of these letters and can't read it, you may forward it to email@example.com and this writer will attempt to decode it for you.
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