As we've shifted from thousands to hundreds of millions of computer
users, much history is lost. Few realize that the backslash character
did not exist in much text usage prior to 1961, and in no computer until
A paper by Eric Fischer, submitted to the Annals of the History of
Computing in early 2000 (and not yet published), unearthed a backslash
on the keyboard of the Teletype Wheatstone Perforator, circa 1937-1945.
But this was unknown to data processing people, who were stuck even up
to the FORTRAN era (beginning 1955) with the Hollerith punch card code.
John Auwaerter, V.P. of Engineering of that same Teletype Corp., and
Chairman of X3, certainly never mentioned it.
Here is the story for the record.
GENESIS IN IBM's STRETCH COMPUTER
As an Algol enthusiast I envisioned a backslash for new computer character
sets, where before and after pairing with the regular slash (or virgule or
slant) could serve for the AND and OR operators of the theoretical Algol
character set. I found the opportunity when invited by Dr. Werner
Buchholz to do the main design of the 120-character set for the Stretch
computer (the IBM 7030). This set, shown on page 12 of , shows both
curly braces, both square brackets, and the reverse slash -- all of which
eventually made their way into 7-bit ASCII.
 shows no ESCape character for STRETCH, for I did not think of that
until after the character set was built into the hardware. There is one
instance of ESCape, in a draft British proposal, for I had by that time
alerted Hugh MacGregor Ross.
We may take it as absolute proof of genesis, from the early limited
character sets, that IBM's STRETCH was the first computer to use the
backslash character, for Reference  was actually published a couple
of years after the design of that machine. And that uniqueness
continued. Reference  shows no 6-bit set with the backslash as a
From Reference :
"I had called a joint meeting of IBM, SHARE, and GUIDE, to regularize
the IBM 6-bit set to become the standard BCD Interchange Code .
Frequency studies of symbol occurrence had been prepared, particularly from
ALGOL programs. The meeting of 1961 July 6 produced general agreement
on a basic 60-64-character set, which included the two square brackets
and the reverse slant, which was chosen in conjunction with "/" to yield
2-character representations for the AND and OR of early ALGOL. This is
reflected in the set I proposed to ANSI X3.2 on 1961 September 18."
(Note: I had put the backslash in position 5/15. It enabled the
ALGOL "and" to be "/\" and the "or" to be "\/".)
SHARE and GUIDE representatives at the meeting were a little stubborn about
accepting my proposed backslash, so I asked for a character more important
to have. After much discussion they could not agree on a better candidate.
"At the 61 November 8-10 meeting, X3.2 constructed the first formal
proposal, X3.2\1 ..." (which, much modified, was
to become ASCII)
(Note: In this proposal the backslash was moved to position 5/12,
and there it has remained ever since.)
Of course the need to use pairs of existing symbols to represent a symbol
not in the set is long past. So the backslash became that most useful of
characters -- one nobody had used or preempted, just waiting there for
a new use. The DOS system that Microsoft bought gave us that use in the
Which is why I refer to the backslash as "my character", together with the
other 10 characters I contributed to ASCII -- see this in
Back to History Index
Back to Home Page
- R.W.Bemer, W.Buchholz, "An extended character set standard",
IBM Tech. Pub. TR00.18000.705, 1960 Jan, rev. TR00.721, 1960 Jun
- R.W.Bemer, "Survey of coded character representation",
Commun. ACM 3, No. 12, 639-641, 1960 Dec
- R.W.Bemer, "A view of the history of the ISO character code",
Honeywell Computer J. 6, No. 4, 274-286, 1972