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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.