Using ~ as a shortcut for home directory...

I just stumbled on the question why tilde (~) is used as a shortcut for home directory on Unix. It's very interesting since it never occurred to me to ask this question? :)

Then, there are lot more questions like that one on StackExchange, here is a selection of some interesting ones (to me at least):

• Why is . and .. used for current and parent directories. The answer isn't so clear as for tilde, but it turned out that hidden files (those whose name begins with a dot) are actually consequence of a bug in early versions of ls command (source and Wikipedia page).
• What does /etc mean?
• What was the shell used before Bourne shell?
• Why is dash (-) used to denote options?
• Why isn't umount spelled unmount?
• What is the origin of 'root' account? But note that this question isn't definitely resolved.
• What is the origin of wheel group name?

And, for the end, here is why vi uses hjkl for cursor movement.

Power supplies...

Have you ever asked yourself how the power supply within you computer works? How complicated it is? Or how did it develop? I never did. For me, it was a black box that takes 220V (or 110V, depending where you live) on input and produces 12V/5V on output. Basically, you don't notice that they exist, but now and then you have some problems caused by them, e.g. when they fail, or when they are not powerful enough.

Today I stumbled on this article about power supplies. I have to say that it is well research article about modern power supplies. It was motivated by Steve Jobs' claim that the power supply within Apple ][ was revolutionary and that the guy that designed it, Rod Holt, didn't get a credit for it. So, the blog's author did an extensive research and found out that Jobs wasn't right. Anyway, I recommend that you read that post, it's very good with a lots of references.

It's interesting how I came accross that post. Initially I stumbled upon a post on Hacker News about some guy that left Google and this Guy explains why. Now, there are different opinions about this topic and maybe I write about it in the future, in the mean time, I found this post about power supplies to be rather interesting.

One more thing. That guy that wrote post about power supplies also wrote a post about iPhone USB charger that he bought cheaply in eBay. What's interesting is that this charger almost certainly doesn't follow safety regulations which means that you can suffer electrical shock. So, don't save money on something that can endanger your life!

A bit more of history...

Well, I wrote about a post in which Rob Landley explains how directory hierarchy within Unix is actually artefact of the shortcoming of the available technology in a specific point in time. And, what's more interesting, not technology in general but in this case creators of Unix didn't have larger disks available to them!

Today, I stumbled on another post, (also here and see here about password "problem" in general) which describes, probably, the first password hack. But reading that post I learned several more things. First, how mail was actually invented before Internet, but also I have read a more detailed history of CTSS system. CTSS was very influential operating system and precursor to Multics, another very influential operating system. I think that knowing at least Multics, could be regarded as a basic knowledge of anyone calling himself a computer scientist or anything similar.

It was also interesting to read how people that made mail were afraid of US postal service. Basically, they thought that this could be regarded as a competition to regular postal service and that they could be fined. I believe that US Postal Service, as well as AT&T, were unimaginable monopolies from today's standpoint. Nevertheless, the same situation was similar in Europe, too. This became clear to me while reading a book about Internet history. First, the fact that AT&T didn't think ARPANet will ever work and thus were not interfering, actually helped ARPANet a lot. On the other hand, Franch PTT actually killed CYCLADES network that had all prerequisites to become the first true Internet.

And while I'm at mail, it is widely regarded that the first spam was sent in 1978, but according to the post about mail, first spam message was an Vietnam anti-war message sent by a MIT engineer who abused his privileges in order to be able to send a message to everyone.

All this, very influential operating systems, electronic mail service, Internet, spam, all that happened in the MIT during 60ties and 70ties. Somehow I wish I had a chance to take part in that, but then again, we still have a chance to do something else. :)

For the end, have you ever wondered when the term device driver was invented? Here is an explanation. Also, here are descriptions of early C compilers and a history of C programming language.

Why we should study history...

Oh, it happened so many times! I stumbled upon it already while reading John Day's book titled Patterns in network architecture: A return to fundamentals. In short, at one point something is controversial and in next, it's regarded as a some kind of a rule that people passionately protect! One good example is 7-layer ISO/OSI Reference Model. When it was created it was problematic how many layers there should be, now, it is taken as something set in stone that there are 7-layers, while in reality it is dubious if this is a correct number. I'm certain that there are a large number of similar examples in every area you can think of. What this implies is that we have to always question the correctness of our current knowledge knowing that something might happen by chance, or politics of a certain time, and that ultimately hampers us from making further progress, maybe even clean start.

And today, I found this post. written by Rob Landley. It's ubeliviable! I'm using Unix/Linux for over 20 years now, always knowing there is a split between /bin, /sbin, /usr/sbin and /usr/bin and knowing why it is done so. But I realise now that, till today, I didn't actually know and, what's more, this is again an example of something that by accident becomes a law. What's more interesting is that not once I stumbled upon some heated discussion about file system layout (an example) in which there were proponents of this split with a simple argument that it is a Unix way of things! Boy, how wrong they are! :)

I'm copying this post here for a refence:

20 years of vim

Wow, I just stumbled on this article on Ars technica (via Hacker News). This article celebrates 20 years of Vim, an vi clone. I have to say I exclusively use vi (Vim actually, but in compatibility mode) for all my editing, or almost all, this post wasn't written in vi. ;)

The first time I used vi was in 1990, or something like that, but it was only for a short period of time when I had an opportunity to work on an Unix system. If I remember correctly it was produced by ICL and it was based on Intel 80386 running on 16MHz.

It's my personal opinion that if you regard yourself an advanced computer user that you either have to learn how to use vi or Emacs (or XEmacs). After all, if you remotely connect to a server, there will be vi, but very probably no gedit, eclipse, or something like that. I strongly believe that in vi I can work more efficiently then in any modern GUI editor. While we are at vi and Emacs, there used to be many flame wars between proponents of vi and those of Emacs. Anyway, I think they are both very good and capable editors. The main Achilles' heel of Emacs was memory consumption, but according to today's measures these are now relatively modest comparing it to some other tools and applications.

Several things I find very interesting in the article about the Vim. The first is a short history of vi editor, among other facts mentioned is that it was written by Bill Joy. Also interesting is the reason why letters hjkl were chosen for moving cursor. Apparently, the terminal used for vi development had arrows on those keys so they were chosen for that reason. But, they proved to be practical and thus were retained until today. Apart from Vim, there were other vi clones of which nvi that ships with BSD operating systems, along with Vim, are the only ones that survived until today. I just checked software repository of Fedora, and there is nvi! I also know that I saw elvis on several occasions, but there is no package in the Fedora repository.

Also, would recommend that you read comments (there are funny ones) and a short history of Vim written by its main author.

The first use of the term "protocol" in networking...

I'm just reading the book Where wizards stay up late - The origins of the Internet and in there I found a statement about the first use of the term protocol to denote the rules to be followed in order for computers to be able to exchange information, i.e. to communicate.

Everything happened in 1965 when Tom Marill, psychologist by formal education, proposed to ARPA an experiment of connecting two machines, TX-2 from Lincoln laboratory at MIT and SDC Q-32 in Santa Monica. Marril founded a company within which he started that experiment but investor backed out and thus Marril turned to ARPA. ARPA agreed to finance experiment, but since Marril's company (Computer Corporation of America - CCA) was too small ARPA also suggested that Lincoln laboratory heads the project. This was accepted and for a project head was appointed Larry Roberts, another Internet pioneer. For the connection itself, a rather primitive modem was used that was able to send 2000 b/s via four-wire full-duplex service leased from Western Union. Marill set up a procedure that composed messages from characters, sent them to other machine and checked if the messages arrived (i.e. waiting for acknowledge). If there was no acknowledge, the message was retransmitted. The set of procedures for sending messages was referred as "message protocol" by Merill, and that is, as far as I know, the first use of that word in such a context. What's interesting is that a colleague apparently asked Marill why he was using that word because it reminds him of diplomacy. Today, word protocol is standard word to denote mechanisms and rules used by computers in order to be able to exchange data.

Anyway, if you know for some earlier use of this word, or more details about this first protocol I would be very interested to here it.

Finally, let me say that the book Where wizards stay up late - The origins of the Internet is a great book about Internet and how it was created. This book is targeted to a less technically knowledgeable people and I strongly recommend it. You can buy one on Amazon, but there are also other services specialize for selling used books, like e.g. AbeBooks. Maybe I'll talk a bit more about that book in some later post.