asciicod.txt

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ASCIICOD.TXT

By Aaron Priven

  This is a little text file for all of the novices out there like myself
who have wandered in on the world of computing eager for knowledge but
who have found very little. This is a table of the ASCII codes.
"What? you ask? The ASCII codes? Why that's easy. 32 is space, and 33 is
the exclamation point, and 34 is the double quote..." All true, except that
the code starts at 0. Well, I imagine that all of you have heard of "NUL"s
or null characters, and probably "NAK"s (which are used in Xmodem Checksum
protocol) but what are the other mysterious codes between 0 and 32?     
 
  Well, friends, this is your opportunity to find out. Because I am going to
tell you. Now don't get the idea that I have been in the computer business
since 1956 and was on the committee that invented the ASCII codes. I wasn't
born till 15 years after that and I got interested in computers two years ago.
I simply stumbled on this very interesting table in the VisiFile manual
(a very bad program marketed by the late lamented VisiCorp that came with my
computer) that not only included the number and two- or three-letter
mnemonic (a fancy "computerish" word for name) but what the codes were
actually intended to do! (Yes, it sounds too good to be true.) So I decided
to gift you all with this table.

  Oh, if you think this is stealing their manual material, for one thing
the ASCII codes are far from copyrighted. And VisiCorp is but a small part of
data in the computer-industry's (read-only?) memory.

And heeeeeeeere's Tabley: 

------------------------------------------------------------------------------
CODE NUMBER   MNEMONIC  WHAT THE HECK IT DOES
------------------------------------------------------------------------------
00            NUL       Null character (nothing)
01            SOH       Start heading
02            STX       Start of text
03            ETX       End of text
04            EOT       End transmission
05            ENQ       Enquiry
06            ACK       Acknowledge (We heard you and yes.) See NAK
07            BEL       Bell (BEEEEEEP!)
08            BS        Backspace
09            HT        Horizontal tab
10            LF        Line feed
11            VT        Vertical tab
12            FF        Form feed (clear screen)
13            CR        Carriage return (enter)
14            SO        Shift-out
15            SI        Shift-in
16            DLE       Data link escape (I don't know what this is either)
17            DC1       Device control #1(maybe they ran out of things to do?)
18            DC2       Device control #2
19            DC3       Device control #3
20            DC4       Device control #4
21            NAK       Negative acknowledge (We heard you, but no.) See ACK
22            SYN       Synchronous idle (let's sit around doing nothing)
23            ETB       End transmission blocks (whatever that means)
24            CAN       Cancel (Whoa, Nellie!)
25            EM        End medium (kill that conjurer!)
26            SS        Special sequence
27            ESC       Escape
28            FS        File separator
29            GS        Group separator
30            RS        Record separator
31            US        Unit separator
32-126        -- Normal characters --
127           DEL       Delete
------------------------------------------------------------------------------

  The parts in parentheses are my own little comments, or explanations.
I still don't know what some of them (the codes) mean. The other thing one
must remember is that these were originally for teletypes and not computers,
so that way "Synchronous idle" and the "Acknowledge" family make more sense.
SYN means that someone doesn't want to do anything just yet. ACK and NAK are
in response to a question. ACK means "Yes, we heard you, and the answer is
yes." NAK means "Yes, we heard you, but the answer is no." Presumably if the
questioner recieves anything else then the questioner means "What?"
  Other ones that make sense to me but might not to other people: ENQ was
more than likely the thing people sent when they wanted an ACK or NAK.
BEL is a bell because electronic speakers on teletypes were not common.
VT probably meant "Go to the next vertical tab row" just as a normal
tab means "Go to the next tab column." FF means to go to the next page;
because there are no pages on a video screen it is interpreted to mean
"Clear the screen." I'm not sure what SI and SO are supposed to do. I
doubt if people would have bothered with other typefaces or compressed
type on the old teletypes. DCx probably means they had four characters
to fill so they put in something meaningless like "Device controls."
"End medium" is a complete mystery to me. SS is of course for codes
relating to things they hadn't thought of at the ASCII committee.
FS,RS,US,and GS I should think would be for a database, but they
didn't put databases on teletypes did they? And why they made DEL all
the way back in the end when they could have just eliminated DC4 or something
is beyond me.


Aaron Priven

If you like this text file, please send 10 cents to the above address.

    Aaron Priven
    540 Sylvan Avenue
    San Mateo, CA 94403-3214
    U.S.A.

Foriegn currency accepted!
e address.
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