[GreenKeys] Done lurking; Teletype model 33 KSR/ASR restoration

[Jim Haynes]

On Thu, 6 Aug 2015, Gil Smith wrote:

> I sorta remember, from my first programming class (fortran) using punch
> cards, that only the first 72 chars were used (I think the last 8 could be
> punched for a sequence number so you could sort your deck if you dropped it,
> or something like that).
> 
I remember that too, and I think it had to do with the IBM 701-704-709
family of machines being 36 bit word length.  The cards were read a row
at a time rather than by columns, so 72 bits of a row fit into two machine
words, and the other 8 columns in a row could not be read.

But I'm sure the concept of 72 character rows is much older.  I remember
from high school typing class that we set the right margin to 72 on a pica
machine, which would have left a right margin of 1.3 inches on standard
paper.  Or maybe we set it to 77 so the bell would ring on 72.

If Univac had prevailed we would have had 90 characters per line rather 
than 80.

I sorta remember early line printers of 120 characters.  In punch card
data processing the data could be packed into the 80 characters of a card,
but for printing you'd want spaces between columns for ease of reading.
So there were plug boards controlling which columns of the printer were
used and which were left blank.  I don't remember if those old 36 bit 
computers could print only 72 columns or if they could print wider.

To relate this to Teletype, I'm not a Real Programmer but I had to write
some code one time for printing on a Model 40 printer or on the IBM
1403 line printer.  Model 40 required a carriage return at the end of the
line.  1403 required a character at the beginning of the line to tell it
to advance to a new line.  And a few of the characters were not 
convertible since the Model 40 was ASCII and the 1403 was EBCDIC.