Kilobytes (KB). Megabytes (MB). Gigabytes (GB).

We use these storage measurements every single, gosh-darned day. And most of us feel like we know exactly what they mean. But do we really?

Do we really — truly — know what a “Byte” is… and its origin? I mean… who came up with the term “Byte”, anyway?

Let’s take a moment to look over the history of the term. If, for no other reason, than to feel smarter than most other nerds.

What is a “Byte”?

If you ask Mr. Google, a Byte is exactly 8 Bits.

Ok. Great. 8 Bits = 1 Byte.

So what is a Bit?

That part is simple.

A Bit is the smallest unit of information for a digital computer. A Bit can have two possible values… 0 or 1. It is a boolean. A binary.

Many people believe “Bit” is short for “Bite”. You find this in many computer history books. This little tidbit has been repeated so often, many believe it. However, like many such oft-repeated anecdotes in computing… it’s hogwash.

In fact, “Bit” is an acronym for “Binary Information Digit”. Squish that phrase together and you get “Bit”.

Fun factoids about the origin of the “Bit”

The first usage of the word “bit”, when talking about a type of data in reference to computing, was by Vannevar Bush. He published an articled entitled “Instrumental Analysis” in the October, 1936 issue of “American Mathematical Society”. In it he used the phrase “bits of information” when talking about punch cards.

However… 

“Bit” was commonly used in Middle English to refer to “a mouthful” or a “morsel” of food. (This is the origin of why many believe “Bit” is short for “Bite”… even though it isn’t.) As such, Vannevar Bush may not have actually been thinking about a “Bit” as a “Binary digit”… instead he may simply have thought “this is a morsel of data”. Also worth noting… Bush never actually defines what a “bit” is. Making it likely that he was simply using the word “bit” in the Middle English way.

The first — distinctly verifiable — usage of “Bit” in this way is by John Tukey. From “A Mathematical Theory of Communication” written by C. E. Shannon in 1949:

“The choice of a logarithmic base corresponds to the choice of a unit for measuring information. If the base 2 is used the resulting units may be called binary digits, or more briefly bits, a word suggested by J. W. Tukey. A device with two stable positions, such as a relay or a flip-flop circuit, can store one bit of information.”

There you have it. More information about the origin of the term “bit” than you ever wanted to know.

You’re welcome.

Ok. Great.

So, in short, a Bit is a 0 or 1. And a Byte is a group of 8 Bits. Easy.

Not so fast there, sport!

While the Byte being 8 Bits is commonly accepted today… that was not always the case. Not by a long shot!

In fact, there are two competing stories for who created the term “Byte”… and neither of them were referring to a set of 8 Bits!

Seriously!

Werner Buchholz’s 6 Bits

The most often cited creator of the term “Byte” is Werner Buchholz — who used the term, in 1956, to refer to a grouping of 6 Bits when working on the IBM Stretch Super computer.

A “6 Bit” Byte was common in those days. In fact, Braille was a 6 Bit encoding of characters for the blind. And many of the early computers (from IBM and others) used 6 Bit groupings to encode character data.

6 Bits -- not 8 Bits -- per Byte.

However (you knew there had to be a “however”)…

Louis G. Dooley’s N Bits

Around that same time (1956 or so), Louis Dooley first used the word “Byte” to refer to an undefined grouping of “Bits”. But, typically, used as “4 Bits”.

That's right.  Not 8 Bits.  Not 6 Bits.  But 4 Bits.

Dooley published the following letter in BYTE magazine:

“I would like to get the following on record: The word byte was coined around 1956 to 1957 at MIT Lincoln Laboratories within a project called SAGE (the North American Air Defense System), which was jointly developed by Rand, Lincoln Labs, and IBM. In that era, computer memory structure was already defined in terms of word size. A word consisted of x number of bits; a bit represented a binary notational position in a word. Operations typically operated on all the bits in the full word.

 

We coined the word byte to refer to a logical set of bits less than a full word size. At that time, it was not defined specifically as x bits but typically referred to as a set of 4 bits, as that was the size of most of our coded data items. Shortly afterward, I went on to other responsibilities that removed me from SAGE. After having spent many years in Asia, I returned to the U.S. and was bemused to find out that the word byte was being used in the new microcomputer technology to refer to the basic addressable memory unit.

 

Louis G. Dooley
Ocala, FL”

So… what the heck is a “Byte”?!

That’s right. We now have two very, very different definitions for the word “Byte”. Both creations of the word happened independently… and at almost the exact same moment in time.

• “The Buchholz Byte” - A grouping of 6 Bits.
• “The Dooley Byte” - A grouping of an undefined number of bits, less than a full word size. Often used to describe 4 Bits.

You’ll note that neither of these definitions — from the men who created the term — have the number “8” in them.

The shift towards 8 Bits per Byte started to happen in the 1970s… with the development and gaining popularity of 8-Bit processors, such as the legendary Intel 8008.

Interestingly, some of those early 8-Bit CPU’s had specific functions for handling 4-Bit chunks of data. Because, up until that point, 4 and 6-Bit “Bytes” were incredibly common (including in the predecessor to the Intel 8008… the 4-Bit Intel 4004).

Fun Factoid: Nowadays a 4-Bit group is called a “Nibble”. Which is adorable.

For quite some time the term “octet” or “octad” was used to denote 8 Bit groups. At some point along the way, most people phased that out as well… simply referring to all “groups of bits” as a “Byte”. Though you will still find “octet” used here and there, especially when talking about various network protocols.

All of which means…

Dooley invented the modern “Byte”… not Buchholz

While many writers, enthusiasts, and computer historians are quick to say that Werner Buchholz coined the term “Byte”… they are obviously mistaken.

Besides the fact that it’s hard to discern who (Dooley or Buchholz) actually used the term first… the Buchholz definition is no longer used at all in modern computing.

The Buchholz definition is specific. 6 Bits. Which modern computing has determined is not the amount of Bits in a modern Byte.

The Dooley definition, on the other hand, allows for wiggle room. Which means that an 8 Bit “Byte” would fit the Dooley definition. But not the Buchholz.

The facts are clear: Louis G. Dooley created the word “Byte”. At least as it has been used for the last 40+ years.

But Buchholz — an absolute legend in the computing world — gets one heck of an Honorable Mention trophy.

Ctrl-Alt-Del — sometimes known as “The Three Fingered Salute” — is among the most recognizable keyboard commands in the entire computer world. Restarting, or logging into, countless computers since the 1980s.

But... what a peculiar combination of keys!  How, exactly, did it come to be?

Let’s take a tour through the history of this beloved / hated / mocked key combination.

Not the first multi-key reset

Control-Alt-Delete may be the most famous “reset this computer” key combination… but it wasn’t the first.

That honor goes to the Exidy Sorcerer in 1978. A Z-80 powered home computer that never saw the commercial success of its rivals.

Note the two “Reset” keys in the top right of the keyboard.

Ok, that simply is too small to make out.

ENHANCE!

Much better.

Here we see the two “Reset” keys.

How do you hard reset an Exidy Sorcerer? You guessed it -- press both of these keys at the same time.

In theory this was to make it harder to accidentally reset a machine... having a single "Reset" key would simply be too easy to tap without intending to.  But they put the two keys immediately next to each other.  And right next to "RETURN" -- which you would always be reaching for with a pinky.  Strange keyboard layout choice, right?

It's like putting a "Nuclear Self Destruct" button right next to the "Make a Cup of Coffee" button.

Regardless, the Sorcerer still wins the title of “first computer with a multi-key reset”. So it’s got that going for it.

The IBM 5150

Flash forward to 1981, in Boca Raton, Florida. A team of engineers was about to release the IBM 5150 (aka “The IBM Personal Computer”).

(Yes. The IBM PC was crated in Florida. That random little tidbit doesn’t get talked about much.)

One of the engineers working on the BIOS of the 5150, David Bradley, implemented a three-key reset for the team within IBM (and partners such as Microsoft) to use during development.

A convenience feature that was never intended to see the light of day. Three keys that would quickly reset the entire machine without needing to do a hard “Power off and Power back on”.

That three-key combination?

Control… Alt… Escape.

“Sorry, Lunduke. You wrote that wrong. It’s Control-Alt-Delete. Not Escape.”

Not at first. In those early days, the key combination was “Ctrl-Alt-Esc”. That’s how the IBM 5150 was originally reset.

However, all three of those keys being on the left hand side of the keyboard made it too easy to accidentally bump.  You might as well have two "RESET" keys right next to each other (how crazy would that be?).

So the lead programmer of the project, Mel Hallerman, suggested changing “Escape” to “Delete” (which was on the complete other side of the keyboard). Thus making it much harder to accidentally hit.

And, just like that, Control-Alt-Delete was born.

It was not supposed to ship

Considering how instantly recognizable the "Three Fingered Salute" is nowadays, it seems wild to think that it was never intended for the public to even know about -- it was strictly for internal development purposes.

In fact, it barely received any development time at all according to the man who developed it.

“It was five minutes, 10 minutes of activity, and then I moved on to the next of the 100 things that needed to get done.” - David Bradley

All that changed when someone included the details of “Ctrl-Alt-Del” in the technical manuals for the IBM Personal Computer.

Here you can see it documented in the “IBM 5150 Guide to Operations” (where it is detailed not once… but three times):

At which point… the cat was out of the bag. Ctrl-Alt-Delete was documented and publicly known (and used) by a commercially successful computer.

There was no turning back now. It was a standard. Even if it was never intended to see the light of day.

And, to think, we were this close to having Ctrl-Alt-Escape instead. (Let’s just thank heavens we didn’t get stuck with the double RESET keys…)

Back in 1984, the Association for Computing Machinery presented Ken Thompson with a “Turing Award” for his many contributions to the world of computing.

And for good reason.

Ken worked on Multics, co-created UNIX, created multiple programming languages (Bon and B — which directly led to C), co-created the Plan 9 operating system, UTF-8, and on and on.  If anyone deserves an award for advancing computing... it's Ken Thompson.

But we’re not here today to talk about those extraordinary contributions to computing.

No, sir.

We’re here to talk… about his acceptance speech.

Because that speech revealed a truly fascinatin computer virus that Thompson had created years earlier… for the C compiler.  One which gave him a backdoor into UNIX itself.

The Speech

He titled his speech “Reflections on Trusting Trust”, and the basic premise is this:

“To what extent should one trust a statement that a program is free of Trojan horses? Perhaps it is more important to trust the people who wrote the software.”

To prove his point, Ken told the tale of how he had — years earlier — created what was, essentially, a computer virus that infected the C compiler (cc) and the UNIX login program.

Seriously.

This is real.

Ken could gain control of most UNIX systems

It worked, essentially, like this:

Ken modified cc (the C compiler on UNIX systems) so that — only when it was compiling UNIX’s “login” program — it would inject a small “backdoor” (into “login”) that would allow him to log in as any user on the system if he used a predefined “password”.

Which is, obviously, a pretty big security hole.

However…

That sort of "universall password" code would be likely to be found during even a rudimentary code review of the C compiler. Or, heck, even by any casual programmer who happened upon that section of the code.

What Ken did next was… devious.

Hiding his UNIX backdoor

He needed to make sure that, should anyone find his nefarious code in “cc”… that his backdoor would live on.

So he then added functionality to “cc” so that it would detect if it was compiling itself (because the C compiler was compiled… in the C compiler)… and insert code into the compiler that would add… itself.

Which means…

Even if the source code is removed from “cc” project… the code (for adding both the login backdoor and the “keep adding this to the C compiler” bits) would get “invisibly” injected into “cc” every time it got compiled by an already infected build of the compiler.

So… as long as there was an unbroken chain of using the C compiler from that point onward, the UNIX login backdoor was unlikely to be effectively removed.

Brutal.

According to Thompson:

“The actual bug I planted in the compiler would match code in the UNIX "login" command. The replacement code would miscompile the login command so that it would accept either the intended encrypted password or a particular known password. Thus if this code were installed in binary and the binary were used to compile the login command, I could log into that system as any user.”

The Moral of the story

As Ken Thompson put it…

“The moral is obvious. You can't trust code that you did not totally create yourself. (Especially code from companies that employ people like me.) No amount of source-level verification or scrutiny will protect you from using untrusted code. In demonstrating the possibility of this kind of attack, I picked on the C compiler. I could have picked on any program-handling program such as an assembler, a loader, or even hardware microcode. As the level of program gets lower, these bugs will be harder and harder to detect. A well installed microcode bug will be almost impossible to detect.”

Did this make it out into the wild?

I know what you're thinking.  "Is this code still out there?  How many systems were impacted by this?"

What we know: This bit of naughty code was released to at least one machine (used by a UNIX support group). This has been confirmed by Ken, himself.

However, it is believed that the code went no further than that machine.

But... do we know for sure?

Do we actually have a high level of confidence that the modified “cc” and “login” went no further than that support group UNIX box?

No. No, we do not.

In fact, according to Eric S. Raymond…

“[I have] heard two separate reports that suggest that the crocked login did make it out of Bell Labs, notably to BBN, and that it enabled at least one late-night login across the network by someone using the login name “kt”.”

BBN.  That's Raytheon.  A critical DARPA researcher -- one which was instrumental in the early days of ARPANET.  A huge amount of software came out of BBN.  Heck, even the first Text Adventure game came from there.

If UNIX machines at Raytheon BBN were infected... the possibility of infected versions of those files making it to other sites is incredibly high.

Truly wild

Which leads to a (rather amusing, and mildly terrifying) bit of historical trivia:

Ken Thompson — one of the co-creators of UNIX — intentionally created a trojan horse that infected both the C compiler and the “login” program of UNIX systems.

What’s more… it went undetected for years.  We wouldn't even have known about it, if he hadn't told us he created it.

And we truly have no clue how widespread that trojan became.