Backing the backslash

I’m almost ashamed to say it, but I never really gave the backslash a second thought.

The backslash’s forward-leaning counterpart is everywhere, especially in computing. It lives in network and web addresses such as https://shadycharacters.co.uk; in file paths, such as /home/keith; and it introduces human-readable “comments” in any number of programming languages, often like /* this */ or // this.

But the backslash? It’s a rarer species. Windows users might recognise it from the command prompt, where it occurs in file paths such as C:\Users\Keith (although Windows does also recognise Unix-style forward slashes). The backslash is also sometimes used to “escape”, or neutralise, characters that would otherwise have some special meaning in a given context. For example, if an ampersand has some special meaning in a particular type of file, prefixing it with a backslash (\&) will often cause it to be treated as a normal ampersand instead. (Ironically, in writing that last sentence I had to escape the backslash character itself, \\, since it has a special meaning in the software that runs shadycharacters.co.uk.)

It was with interest, then, that I read a post on Mastodon* from a user named Modulux on the subject of the backslash:

Friend of mine was commenting that the origins of the backslash character are unclear. It was included in the teletype character set and IBM put it on ASCII for that reason but it is not known what it was for. Searching around I found some unreliable info that it was used in typography from the 16th century in order to represent line or paragraph breaks. Can anyone confirm or disconfirm, preferably with source?

To set one thing straight, the backslash wasn’t historically used for line or paragraph breaks. Instead, that was one of the functions of the forward slash, which, once upon a time, had an important role in punctuating texts: in the medieval and early modern periods, a forward slash could be used to indicate a pause of a lesser or greater length, anywhere between a comma and a paragraph depending on its user. It was often called a virgula or virgule, and it gave rise to the modern comma. It is covered along with many other such marks in the Shady Characters book.

Virgules in the prologue to William Caxton's edition of Virgil's Eneydos
Virgules in the prologue to William Caxton’s edition of Virgil’s Eneydos. (CC-BY 2.0 image courtesy of the University of Glasgow.)

Historical wobbles aside, on the question of where the backslash, or ‘\’, had come from, a lively discussion ensued. Stewart Russell responded:

According to Mackenzie (“Coded Character Sets, History and Development”) it seems to have appeared in the IBM Stretch design proposal, sometime in the mid 1950s (even though the first Stretch machine was delivered to Los Alamos in 1961) – see the chapter “Early Codes”, around page 80. The first name given to it was “Reverse Divide”.

It was also used in the text representation of ALGOL, with /\ for “∧” (AND) and \/ for “∨” (OR).

I had picked up a copy of Charles Mackenzie’s Coded-character Sets: History and Development during the writing of Shady Characters (never say writing isn’t a glamorous occupation), so I looked up Stewart’s reference. And indeed, the modern backslash does seem to have appeared first in IBM’s so-called Stretch character set,1 as used in an eponymous computer delivered to Los Alamos National Laboratory† in 1961.2

I talk more about character sets in my upcoming book, Face with Tears of Joy, but the long and short of it is that character sets are lexicons of individual characters known to one computer or another. To communicate successfully, any two computers must agree on which character set to use. Nowadays, that is a very simple negotiation, since effectively all computers use the all-encompassing Unicode character set. Back in the ’50s, however, things were different — electronic computers were still new, and many of them boasted their own specialised character sets. IBM’s Stretch computer was a case in point.

Why, though, had IBM chosen to incorporate a backslash in this new character set? Even before the Stretch computer had been delivered to Los Alamos, an influential IBMer named Bob Bemer3 had written to the Association of Computing Machinery, the industry body for America’s computer manufacturers and computer scientists, to make the case for developing a standard character set.4 His proposal kickstarted a drive towards just such a standard, and eventually resulted in the creation of ASCII — the American Standard Code for Information Interchange, a forerunner of Unicode, and whose name you may well have heard before.

Yet Bemer also had his day job at IBM, and one of his tasks there was to figure out which characters should be available on the as-yet unfinished Stretch computer.5 Enter the backslash — or rather, enter the “reverse divide” character, which is what Bemer had called it in his 1959 paper for the ACM.4

Before his death in 2004, Bemer wrote an short article entitled “How ASCII Got its Backslash” on, well, how ASCII got its backslash, and it does not have a lot to do with division, reverse or otherwise. Bemer recalls that he wanted to be able to write certain logical expressions in a programming language called Algol.6 At the time, Algol was still very new, though it had already been anointed by the ACM as its standard language for computer algorithms. Among other things, Algol allowed programmers to use binary logic, in which values could be combined and manipulated using operations called AND, OR and NOT. The first of those two operations were typically written using A- and V-shaped characters (‘∧’ and ‘∨’ respectively), and Algol adopted that same convention.7

The problem, as Bemer saw it, was that extant character sets had no way to render those crucial Boolean operations. Being all too aware of the limited memory available to early computers, Bemer realised that with the addition of a single new character — ‘\’ — he could write Algol’s AND and OR operators by combining it with the ‘/’ already present in many other character sets: /\, \/.6 Thus the backslash appeared, first for use by programs running on the Stretch computer and later in ASCII itself.

As to the name of the ‘\’; well, it’s all a little unsatisfying. In his earliest published writing on the subject, that 1959 article for the ACM, Bemer calls the backslash the “reverse divide”.4 His reasoning is obvious enough — ‘\’ is the mirror image of ‘/’, which is commonly used to indicate mathematical division — although he never spelled it out as such. “Reverse slant” is another early favourite, again for fairly obvious reasons, cropping up in a contemporary account of the IBM Stretch project8 and going on to eclipse “reverse divide” in popularity. The existence of two different names would suggest that ‘\’ had no commonly-held name at the time, and that a new one had had to be invented.

Yet neither name would last very long. Soon after Bemer minted the ‘\’, some anonymous programmer decided that “reverse slant” and “reverse divide” were too wordy, or too obscure, and came up with a pithier name for it. Born in the ’50s as the “reverse divide”, in the ’60s the ‘\’ was reinvented as the “backslash”‡ (who wasn’t reinventing themselves in that decade?), and the name has stuck ever since.

Except, except! That is not the whole story. The backslash, it turn out, is a few decades older than it seems — or rather, it has a doppelganger from an earlier technological era. There’s an intriguing story behind that one too, but it will have to wait for another time!

1.
MacKenzie, Charles E. “Early Codes : The Stretch Code”. In Coded Character Sets: History and Development, 67-75. Addison-Wesley Pub (Sd), 1980.

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2.
CHM Revolution. “IBM Stretches Its Capabilities”. Accessed March 13, 2025.

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3.
Hardison, Erica. “Robert W. Bemer”. IEEE Computer Society.

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4.
Bemer, R. W. “A Proposal for a Generalized Card Code for 256 Characters”. Commun. ACM 2, no. 9 (September 1, 1959): 19–23. https://doi.org/10.1145/368424.368435.

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5.
Bemer, Bob. A Story of ASCII.

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6.
Bemer, Bob. “How ASCII Got Its Backslash”.

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7.
Perlis, A. J., and K. Samelson. “Report on the Algorithmic Language ALGOL the ACM Committee on Programming Languages and the GAMM Committee on Programming”. Numerische Mathematik 1, no. 1 (December 1959): 41-60. https://doi.org/10.1007/BF01386372.

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8.
Ballance, Richard S., and Werner Buchholz. “Chapter 6: Character Set”. In Planning a computer system; Project Stretch. New York: McGraw-Hill, 1962.

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*
This is a convenient simplification: Modulux posted on a personal server compatible with Mastodon but not actually running Mastodon itself — so although I first read Modulux’s post on Mastodon, it did not originate there. This is the strength of the so-called fediverse, where anyone can run a social network and connect it, or “federate”, to other networks. It’s a bit like email — you can use one of the big providers such as Gmail or Apple iCloud, or you can run your own personal mail server. It is a brave new world, and a welcome one, too. Shady Characters also lives there, at mastodon.social/@shadychars. ↢
†
Nuclear energy once again! This is turning into a theme. ↢
‡
Google Ngrams shows 1967 as the inflection point. ↢

Miscellany № 106: pistols, punctuation and print

I came across a post last July on Emojipedia, in which Keith Broni* noted that Twitter, or X, had redesigned its PISTOL emoji. PISTOL had always been controversial: most online platforms started off with PISTOLs drawn as realistic firearms, but, over the course of the mid-2010s, most of them moved to toylike renderings of water pistols instead. Twitter had followed suit.

Last year, though, as Broni reported, Twitter’s water pistol was redrawn to show a realistic, if simplified, handgun. There doesn’t seem to have been a great deal of fanfare from Twitter itself, or any formal justification for why the change was made. Which is, perhaps, not a surprise, since Elon Musk fired Twitter’s PR team soon after he became CEO in 2022. There’s no-one left to announce anything.

Ordinarily, I would have dismissed this news as relatively small beer. Emoji are redesigned all the time, even if usually not in quite such a radical fashion. Moreover, Elon Musk has always been a contrarian, and his increasingly hard-right rhetoric† often seemed calculated more to enrage than to persuade — and was, as such, easy to ignore.

Now, though, as I witness the political turmoil gripping the USA, and I bear in mind that Elon Musk is one of its fiercest cheerleaders, I wonder if that small but significant change to a single emoji is more important than I once thought. When it’s published this July, Face With Tears of Joy will talk about how emoji can change appearances and meanings — and indeed, it takes the PISTOL as a case study — but Twitter’s mean-spirited update to ‘🔫’ is almost painfully relevant. The renewed presence of a realistic pistol emoji on an ailing but still relevant social network seems in hindsight to have been a harbinger of something much worse coming down the line.

In an attempt to lighten the mood, may I present a short extract from Yuyn Li’s short story, “Apostrophe’s Dream”, part of a collection called A Cage Went in Search of a Bird:

colon: Ah, yes, friends, let me remind you all: we have been discussing the pressing issue of relevance. We are, unlike letters and numbers, increasingly facing a fate of being misused, abused, and worse, rejected as being superfluous.
 
comma: Tell that to my Oxford cousin—he’s the most unflappable creature but that doesn’t help in his case. Half—no, more than half—of the world don’t even know of his existence these days.

Yes: this is indeed a conversation between punctuation marks, and I am not spoiling it too greatly if I tell you to expect the ellipsis, exclamation mark, period and other marks to weigh in too. Read the full story at The Dial!

Lastly, podcast fans should listen to this recent episode of Grammar Girl, entitled “Cancellation”. Mignon Fogarty, the host, explains why the American spellings of “cancellation” and “canceled” use a double and single l respectively, which is interesting enough in itself, but do hang around for the second part of the show, in which Mignon reads a short essay by Glenn Fleishman on the origins of the term “fine print”. It’s a fact-filled summary of more than four centuries of printing history.

Enjoy!

*
From one Keith to another, 🤜🤛. ↢
†
Rhetoric which has caused me and many others to shut down our Twitter accounts either temporarily or permanently. If you’d like to follow Shady Chracters on social media, please see the alternative links in the colophon. ↢

Complying with the Online Safety Act

In October 2023, the UK government passed into law the Online Safety Act, a set of regulations intended to make online services more responsible for the content they carry. It is a laudable aim, but unfortunately the distinctions the Act draws between large sites such as Facebook and Google and smaller sites such as this one are insufficiently well defined. The upshot is that complying with the Act places a much larger burden on the owners of sites such as Shady Characters than it does on the owners of those larger sites.

Compounding the problem is that the guidance provided by Ofcom, the UK telecoms regulator, is not entirely clear on exactly which sites must comply with the Act. The good news, inasmuch as I understand the Act and its consequences, is that Shady Characters is already very close to being a site which does not need to comply. Commenters cannot upload images, which removes one vector for potentially offensive or graphic content. Problematic textual comments are generally caught by moderation filters, and the volume of comments is low enough so that I can read and respond to each one individually — and remove or edit them if necessary.

The one feature that does fall foul of the act is the ability for commenters to reply to one another. From the OSA’s perspective, this makes Shady Characters into a “user-to-user” service, which would bring it under the purview of the Act. As such, I will be removing the ability to reply to other users’ comments from today onwards. (Existing comments and replies will be retained.) I’m sorry that this has to be done, but I don’t think I have a great deal of choice.

I’ll be keeping abreast of news about the OSA and how smaller sites must comply with it, and it may be that I can reenable replies at some point in the future. For now, though, thank you for reading (and commenting!), and I hope that this doesn’t affect your enjoyment of the site too greatly.

Shady Characters on AMSEcast: a podcast about calculators

I’ve had nuclear energy on the mind recently — a product of watching Oppenheimer, perhaps, and also the UK government’s newfound interest in nuclear power in the interest of combatting climate change. Apropos of all that, then, I was happy to appear on a recent episode of AMSEcast, the podcast of the American Museum of Science and Energy in Oak Ridge, Tennessee. The episode was hosted by the museum’s director, the genial Alan Lowe, who was kind enough to let me rabbit on at length on the subjects of counting, calculators, and computers. I really enjoyed talking to Alan, and I hope you enjoy listening too!

Miscellany № 105: blog questions challenge

There is something interesting happening with blogging. For a long time, blogs like this one were the way to opine, to share, to bloviate. Then social media came along and stole blogging’s thunder, with the average blogger gravitating towards long threads on Twitter (RIP; † ⚰; 💀; etc., etc.) or photo-heavy Instagram posts. Next came newsletters — blogs delivered by email, essentially — which finally broke the social media hegemony.

And yet, neither social media nor newsletters have ever had quite the same vibe as blogging. If you rely on social media, your posts live or die by how well they attract outrage or sympathy. If you rely on newsletters, you may be inadvertently rubbing shoulders with Nazis. In either case, the continued existence of your “platform” — your social media posts, your newsletters — depends on the whims of a company with its interests at heart, not yours.

All this is to say that I am very happy to see that blogging is having a bit of a moment, as exemplified by the so-called Blog Questions Challenge. This is a kind of internet chain letter, started by Scott Boms* on his own blog, “Documenting”, and to which I am rudely attaching myself without having been invited. The idea is that bloggers answer a few questions about where their blogs came from, how they work, and where they’re going. As such, I present to you the Shady Characters edition of the Blog Questions Challenge.

Why did you start blogging in the first place?

I wanted to write. I’m not entirely sure why, but I read a lot as a kid and books seemed to be important in some slightly mysterious way.

I eventually had an idea that there might be something interesting about the more unusual typographical marks I sometimes came across — ¶ @, *, † § and others — which led me to write what I hoped might become the constituent chapters of a book on the subject.

Having written those “chapters”, though, I didn’t really know what to do with them. Email a literary agent? A publisher? That seemed very forward, so I started Shady Characters instead and have been writing here ever since. (The agent and the publisher came along later, so it all turned out alright in the end.)

What platform are you using to manage your blog and why did you choose it?

I’ve used WordPress all this time — almost exactly thirteen years now. It seemed like the best option at the time, with endless scope for customisation and a robust network of supporters from whom to get help and inspiration.

WordPress comes in open source and commercial flavours. The first, where you have to install and administer WordPress yourself, is what I use. The second, where a commercial company such as WordPress.com or WPEngine handles all of that for you, always seemed like a very expensive way to go about things.

Now, though, WordPress’s open source and commercial faces are coming into conflict. Matt Mullenweg, who co-founded WordPress in 2003 and has maintained the air of a benevolent dictator since then, seems to be suffering from early-onset tech leader derangement. (Perhaps it’s catching.) Mullenweg has argued that for-profit companies (his own aside, of course) which benefit from WordPress’s freely available source code should be contributing more to that same source code, despite there being no legal compulsion to do so. The resulting ructions in the WordPress world have not been reassuring.

Have you blogged on other platforms before?

I used Google’s Blogspot for a personal diary a long, long time ago.

When do you feel most inspired to write?

I am not, it is fair to say, a natural writer. I have to treat it more like a job: set up a schedule and stick to is as closely as I can, family and other obligations notwithstanding. To fuel my miscellany posts, I keep a list of interesting websites, news stories and other articles as inspiration. Occasionally, though, something will pop up that I need to write about. A recent post on generative AI was one instance of that; an exploration on statistical frequency of punctuation marks was another.

Do you publish immediately after writing, or do you let it simmer a bit as a draft?

Occasionally, I’ll still be trying to figure out what a post is actually about as I’m in the middle of writing it. In those cases, there will be an extended period of writing and rewriting. Most other posts I publish as soon as I’ve finished them.

What are you generally interested in writing about?

I thought about this recently. For a long time, the header on the Shady Characters home page told readers to expect “un­usual marks of punc­tu­ation, books and book his­tory, and everything in between”. Now, though, with the publication of Empire of the Sum behind me and Face with Tears of Joy coming up this summer, things aren’t so clear-cut. For the moment, I’ve settled on this: “unorthodox information technologies”. I’m not sure it conveys exactly what I want it to, but it’s close enough.

Who are you writing for?

Hmm. Hmm. I would like to say that I’m writing for posterity — to help collate and collect stories, facts and other bits of information that deserve to be shown to a wider audience. But if I’m honest with myself, I’m writing for me — I’m writing because I enjoy the craft and the habit of it, and because each word written by a human being is another blow struck against the entropy of the universe. (I’m a lapsed physicist, in case it isn’t obvious.)

What’s your favorite post on your blog?

I honestly don’t know! Have a look at the Contents page and let me know what your favourite post is in the comments.

Any future plans for your blog? Maybe a redesign, a move to another platform, or adding a new feature?

In writing terms, I’d like to get back to a more regular cadence, which will be easier once the kids are a little older.

In design terms, I’ll be sticking with this design for a while longer. You can see the original one on archive.org; it lasted for around six years, and the current design is now pushing eight. Even so, I’m quite proud of it and I have no plans to change it any time soon.

The one thing I would like to change is the WordPress software that underpins the blog. It’s written in a programming language called PHP that I don’t especially enjoy using, and the shenanigans at the top of the WordPress community do not inspire confidence in WordPress itself. Grupetto.cc, my (very) occasional cycling blog, uses a system called Eleventy. It’s simpler and more flexible than WordPress, and I’ve been plotting a move to it for Shady Characters for a while. Time will tell when that happens.

Next?

Might I tag in Glenn Fleishman or Doug Wilson to give us their answers to these questions?

Thanks for reading!

*
Here are a few more examples from Jon Hicks, Rachel Andrew, Jasper Tandy and Aegir Hallmundur. ↢